Podcasts about functor

Steve and Graham are back for more frivolity to discuss Cities Skylines 2, technical difficulties, and the upcoming releases of November, with some Must Listens sprinkled on top! Show Segments: 00:00 - Intro 04:15 - Graham's Games 55:46 - Steve's Games 1:27:04 - Beginning of the End Games Mentioned: Assassin's Creed Mirage Cities: Skylines II Cocoon Sea of Stars Mortal Kombat 1 Wo Long: Fallen Dynasty Subpar Pool Par for the Dungeon Lapin Alien: Isolation Hexarchy Episode's YouTube Video SIPTG YouTube Channel: https://www.youtube.com/c/shouldiplaythisgamequestionmark Music by Kevin MacLeod: https://incompetech.com/music

Lambda Kalkül, Functor, Monad - oft wird es erstmal akademisch, wenn man dem Thema "Funktionale Programmierung" das erste mal begegnet und nicht selten schwillt einem dann erstmal der Kopf. In dieser Ausgabe des Sandpapiers versuchen sich Martin und Theo daran, die Grundlagen von Functional Programming möglichst einfach zu erklären und dabei auf zu viel komplizierten Jargon zu verzichten. Falls ihr Fragen oder Anregungen habt, immer her damit: Martin auf Twitter: @felbit Theo auf Twitter: @on3iro Sandstorm auf Twitter: @sandstormmedia Oder schreibt uns eine Mail an kontakt@sandstorm.de Das Sandpapier ist ein wöchentlicher Podcast der Sandstorm Media GmbH. Wir erzählen aus unserem Alltag, was wir versuchen, anders zu machen und welchen Herausforderungen und Experimenten wir uns auf unserem Weg stellen.

Functors are an operation that has a structure preserving property. But what is that? Are these things practical? Does it have anything to do with the real world? Of course! To be useful, it must derive from real-world things we see all around us. This one is an assembly line. How? That’s what this episode is all about.

Fredrik talks to Bartosz Milewski - programmer, writer and creator of mind-expanding presentations - about a wide range of things in the lands between mathematics and programming. Bartosz explains his increasing interest in mathematics, type and category theory and why he thinks mathematics and programming can and are coming closer together. We eventually get to the topic of Bartosz' talk last year, and perhaps the only way humans can understand things and how that affects what we discover. Perhaps even what we are able to discover. Recorded on stage at Øredev 2018. Thank you Cloudnet for sponsoring our VPS! Comments, questions or tips? We are @kodsnack, @tobiashieta, @oferlund and @bjoreman on Twitter, have a page on Facebook and can be emailed at info@kodsnack.se if you want to write longer. We read everything we receive. If you enjoy Kodsnack we would love a review in iTunes! Links Øredev 2018 Bartosz Milewski Bartosz' presentation the day before - Programming with math Bartosz’s second presentation of the year is unfortunately not online yet Type theory Category theory Template metaprogramming Cateogry theory for the working mathematician Functor Monad Richard Feynman Category theory for programmers Bartosz' videos on Youtube Quadratic equations Fermat’s last theorem and the proof Homotopy type theory The Curry-Howard isomorphism Bartosz' talk from last year - The earth is flat Titles I skipped a lot of slides Something related to math Pushed by external forces What is fascinating to me at the moment Tone down the category theory I’m really comfortable with math I discovered a whole new franchise I read a few first sentences The idea of category theory is not that difficult Multiply and divide things for months This gap between programming and math (There is) A lot of commonality How to split things and how to compose them The science of composition We humans have to structure things The different ways of splitting things Mathemathics is the future Who wants to program in assembly language Test-driven proof development A lot of hand-waving in math as well Mechanizing proofs An outgowth of type theory The only way we humans can understand nature Life can only exist in a decomposable environment Our brains work by decomposing things Why would there be a simple solution?

Tracy Lee: @ladyleet | ladyleet.com Ben Lesh: @benlesh | medium.com/@benlesh Show Notes: 00:50 - What is This Dot? 03:26 - The RxJS 5.5.4 Release and Characterizing RxJS 05:14 - Observable 07:06 - Operators 09:52 - Learning RxJS 11:10 - Making RxJS Functional Programming Friendly 12:52 - Lettable Operators 15:14 - Pipeline Operators 21:33 - The Concept of Mappable 23:58 - Struggles While Learning RxJS 33:09 - Documentation 36:52 - Surprising Uses of Observables 40:27 - Weird Uses of RxJS 45:25 - Announcements: WHATWG to Include Observables and RxJS 6 Resources: this.media RxJS RX Workshop Ben Lesh: Hot vs Cold Observables learnrxjs.io RxMarbles Jewelbots Transcript: CHARLES: Hello everybody and welcome to The Frontside Podcast, Episode 91. My name is Charles Lowell, a developer here at The Frontside and your podcast host-in-training. Joining me today on the podcast is Elrick Ryan. Hello, Elrick. ELRICK: Hey, what's up? CHARLES: Not much. How are you doing? ELRICK: I'm great. Very excited to have these two folks on the podcast today. I feel like I know them… CHARLES: [Laughs] ELRICK: Very well, from Twitter. CHARLES: I feel like I know them well from Twitter, too. ELRICK: [Laughs] CHARLES: But I also feel like this is a fantastic company that is doing a lot of great stuff. ELRICK: Yup. CHARLES: Also not in Twitter. It should be pointed out. We have with us Tracy Lee and Ben Lesh from This Dot company. TRACY: Hey. CHARLES: So first of all, why don't we start, for those who don't know, what exactly is This Dot? What is it that you all do and what are you hoping to accomplish? TRACY: This Dot was created about a year ago. And it was founded by myself and Taras who work on it full-time. And we have amazing people like Ben, who's also one of our co-founders, and really amazing mentors. A lot of our friends, when they refer to what we actually do, they like to call it celebrity consulting. [Laughter] TRACY: Which I think is hilarious. But it's basically core contributors of different frameworks and libraries who work with us and lend their time to mentor and consult with different companies. So, I think the beautiful part about what we're trying to do is bring together the web. And we sort of do that as well not only through consulting and trying to help people succeed, but also through This Dot Media where it's basically a big playground of JavaScripting all the things. Ben and I do Modern Web podcast together. We do RX Workshop which is RxJS training together. And Ben also has a full-time job at Google. CHARLES: What do they got you doing over there at Google? BEN: Well, I work on a project called Alkali which is an internal platform as a service built on top of Angular. That's my day job. CHARLES: So, you've been actually involved in all the major front-end frameworks, right, at some point? BEN: Yeah, yes. I got my start with Angular 1 or AngularJS now, when I was working as a web developer in Pittsburgh, Pennsylvania at a company called Aesynt which was formerly McKesson Automation. And then I was noticed by Netflix who was starting to do some Angular 1 work and they hired me to come help them. And then they decided to do Ember which is fine. And I worked on a large Ember app there. Then I worked on a couple of large React apps at Netflix. And now I'm at Google building Angular apps. CHARLES: Alright. BEN: Which is Angular 5 now, I believe. CHARLES: So, you've come the full circle. BEN: Yeah. Yeah, definitely. CHARLES: [Chuckles] I have to imagine Angular's changed a lot since you were working on it the first time. BEN: Yeah. It was completely rewritten. TRACY: I feel like Angular's the new Ember. CHARLES: Angular is the new Ember? TRACY: [Laughs] BEN: You think? TRACY: Angular is the new Ember and Vue is the new AngularJS, is basically. [Laughs] CHARLES: Okay. [Laughter] CHARLES: What's the new React then? BEN: Preact would be the React. CHARLES: Preact? Okay, or is Glimmer… BEN: [Laughs] I'm just… CHARLES: Is Glimmer the new React? BEN: Oh, sure. [Laughs] CHARLES: It's important to keep these things straight in your head. BEN: Yeah, yeah. CHARLES: Saves on confusion. TRACY: Which came first? [Chuckles] BEN: Too late. I'm already confused. CHARLES: So now, before the show you were saying that you had just, literally just released RxJS, was it 5.5.4? BEN: That's right. That's right. The patch release, yeah. CHARLES: Okay. Am I also correct in understanding that RxJS has kind of come to very front and center position in Angular? Like they've built large portions of framework around it? BEN: Yeah, it's the only dependency for Angular. It is being used in a lot of official space for Angular. For example, Angular Material's Data Table uses observables which are coming from RxJS. They've got reactive forms. The router makes use of Observable. So, the integration started kind of small which HTTPClient being written around Observable. And it's grown from there as people seem to be grabbing on and enjoying more the React programming side of things. So, it's definitely the one framework that's really embraced reactive programming outside of say, Cycle.js or something like that. CHARLES: Mmhmm. So, just to give a general background, how would you characterize RxJS? BEN: It's a library built around Observable. And Observable is a push-based primitive that gives you sets of events, really. CHARLES: Mmhmm. BEN: So, that's like Lodash for events would be a good way to put it. You can take anything that you can get pushed at you, which is pretty much value type you can imagine, and wrap it in an observable and have it pushed out of the observable. And from there, you have a set of things that you can combine. And you can concatenate them, you can filter them, you can transform them, you can combine them with other sets, and so on. So, you've got this ability to query and manipulate in a declarative way, events. CHARLES: Now, Observable is also… So, when Jay was on the podcast we were talking about Redux observable. But there was outside of the context of RxJS, it was just observables were this standalone entity. But I understand that they actually came from the RxJS project. That was the progenitor of observables even though there's talk of maybe making them part of the JavaScript spec. BEN: Yeah, that's right. That's right. So, RxJS as it stands is a reference implementation for what could land in JavaScript or what could even land in the DOM as far as an observable type. Observable itself is very primitive but RxJS has a lot of operators and optimizations and things written around Observable. That's the entire purpose of the library. CHARLES: Mmhmm. So, what kind of value-adds does it provide on top of Observable? If Observable was the primitive, what are the combinators, so to speak? BEN: Oh, right. So, similar to what Lodash would add on top of say, an iterable or arrays, you would have the same sorts of things and more inside of RxJS. So, you've got zip which you would maybe have seen in Lodash or different means of combines. Of course, map and ‘merge map' which is like a flattening sort of operation. You can concatenate them together. But you also have these time-based things. You can do debouncing or throttling of events as they're coming over in observable and you create a new observable of that. So, the value-add is the ability to compose these primitive actions. You can take on an observable and make a new observable. We call it operators. And you can use those operators to build pretty much anything you can imagine as far as an app would go. CHARLES: So, do you find that most of the time all of the operators are contained right there inside RxJS? Or if you're going to be doing reactive programming, one of your tasks is going to be defining your own operators? BEN: No, pretty much everything you'd need will be defined within RxJS. There's 60 operators or so. CHARLES: Whoa, that's a lot. BEN: It's unlikely that someone's going to come up with one. And in fact, I would say the majority of those, probably 75% of those, you can create from the other 25%. So, some of the much more primitive operators could be used… TRACY: Which is sort of what Ben did in this last release, RxJS 5…. I don't know remember when you introduced the lettable operators but you… BEN: Yeah, 5.5. TRACY: Implemented [inaudible] operators. BEN: Yeah, so a good portion of them I started implementing in terms of other operators. CHARLES: Right. So, what was that? I didn't quite catch that, Tracy. You said that, what was the operator that was introduced? TRACY: So, in one of the latest releases of RxJS, one of the more significant releases where pipeable operators were introduced, what Ben did was he went ahead and implemented a lot of operators that were currently in the library in terms of other operators, which was able to give way to reduce the size of the library from, I think it was what, 30KB bundled, gzipped, and minified, to about 30KB, which was about 60 to 70% of the operators. Right, Ben? BEN: Yeah. So, the size reduction was in part that there's a lot of factors that went into the size reduction. It would be kind of hard to pin it down to a specific operator. But I know that some of the operators like the individual operators themselves, by reimplementing reduce which is the same as doing as scan and then take last, implementing it in terms of that is going to reduce the size of it probably 90% of that one particular file. So, there's a variety of things like that that have already started and that we're going to continue to do. We didn't do it with every operator that we could have. Some operators are very, very common and consequently we want them to be as optimized as possible. For example, map. You can implement map in terms of ‘merge map' but it would be very slow to do so. It might be smaller but it would be slower. We don't want that. So, there are certain areas we're always going to try to keep fairly a hot path to optimize them as much as possible. But in other spots like reduce which is less common and isn't usually considered to be a performance bottleneck, we can cut some corners. Or ‘to array' or other things like that. CHARLES: Mmhmm. TRACY: And I think another really interesting thing is a lot of people when learning RxJS, they… it's funny because we just gave an RX Workshop course this past weekend and the people that were there just were like, “Oh, we've heard of RxJS. We think it's a cool new thing. We have no plans to implement it in real life but let's just play around with it and let me learn it.” I think as people are starting to learn RxJS, one of the things that gets them really overwhelmed is this whole idea that they're having to learn a completely new language on top of JavaScript or what operators to use. And one of our friends, Brian Troncone who is on the Learning Team, the RxJS Learning Team, he pulled up the top 15 operators that were most commonly searched on his site. And some of them were ‘switch map', ‘merge map', ‘fork join', merge, et cetera. So, you can sort of tell that even though the library has quite a few… it's funny because Ben, I think the last RX Workshop you were using pairs and you had never used it before. BEN: Yeah. TRACY: So, it's always amusing for me how many people can be on the core team but have never implemented RxJS… CHARLES: [Laughs] TRACY: A certain way. BEN: Right. Right, right, right. CHARLES: You had said one of the recent releases was about making it more friendly for functional programming. Is that a subject that we can explore? Because using observables is already pretty FP-like. BEN: What it was before is we had dot chaining. So, you would do ‘dot map' and then call a method and then you get an observable back. And then you'd say ‘dot merge' and then you'd call a method on that, and so on and so forth. Now what you have is kind of a Ramda JS style pipe function that just takes a comma-separated list of other functions that are going to act upon the observable. So, it reads pretty much the same with a little more ceremony around it I guess. But the upside is that you can develop your operators as just higher-order functions. CHARLES: Right. And you don't have to do any monkey-patching of prototypes. BEN: Exactly, exactly. CHARLES: Because actually, okay, I see. This is actually pretty exciting, I think. Because we actually ran into this problem when we were using Redux Observable where we wanted to use some operators that were used by some library but we had to basically make a pull request upstream, or fork the upstream library to include the operators so that we could use them in our application. It was really weird. BEN: Yeah. CHARLES: The reason was because it was extending the observable prototype. BEN: Yeah. And there's so many… and that's one way to add that, is you extend the observable prototype and then you override lift so you return the same type of observable everywhere. And there are so many things that lettable operators solved for us. For example… CHARLES: So, lettable operators. So, that's the word that Tracy used and you just used it. What are lettable operators? BEN: Well, I've been trying to say pipeable and get that going instead of lettable. But basically there's an operator on RxJS that's been there forever called let. And let is an operator and what you do is you give it a function. And the function gives you the source observable and you're expected to return a new observable. And the idea is that you can then write a function elsewhere that you can then compose in as though it were an operator, anywhere you want, along with your other dot-chained operators. And the realization I had a few months ago was, “Well, why don't we just make all operators like this?” And then we can use functional programming to compose them with like a reduce or whatever. And that's exactly what the lettable operators are. And that's why I started calling them lettable operators. And I kind of regret it now, because so many people are saying it and it confuses new people. Because what in the world does lettable even mean? CHARLES: Right. [Laughs] BEN: So, they are pipeable operators or functional operators. But the point is that you have a higher-order function that returns a function of a specific shape. And that function shape is, it's a function that receives an observable and returns an observable, and that's it. So, basically it's a function that transforms an observable into a new observable. That's all an operator. That's all an operator's ever been. It's just this is in a different flavor. CHARLES: Now, I'm curious. Why does it do an observable into an observable and not a stream item into an observable? Because when you're actually chaining these things together, like with a map or with a ‘flat map' or all these things, you're actually getting an individual item and then returning an observable. Well, I guess in this case of a map you're getting an item and returning an item. But like… BEN: Right, but that's not what the entire operation is. So, you've got an operation you're performing whenever you say, if you're to just even dot-chain it, you'd say ‘observable dot map'. And when you say ‘dot map', it returns a new observable. And then you say ‘dot filter' and it returns another new observable. CHARLES: Oh, gotcha, gotcha, gotcha. Okay, yeah, yeah, yeah. Yeah, yeah. BEN: So, this function just embodies that step. CHARLES: I see, I see. And isn't there some special… I feel like there's some proposal for some special JavaScript syntax to make this type of chaining? BEN: Yeah, yeah, the pipeline operator. CHARLES: Okay. BEN: I don't know. I think that's still at stage one. I don't know that it's got a lot of headway. My sources and friends that are in the TC39 seem to think that it doesn't have a lot of headway. But I really think it's important. Because if you look at… the problem is we're using a language where the most common use case is you have to build it, get the size as small as possible because you need to send it over the wire to the browser. And understandably, browsers don't want to implement every possible method they could on say, Array, right? CHARLES: Mmhmm, right. BEN: There's a proposal in for ‘flat map'. They could add zip to Array. They could add all sorts of interesting things to Array just by itself. And that's why Lodash exists, right? CHARLES: Right. BEN: Is because not everything is on Array. And then so, the onus is then put on the community to come up with these solutions and the community has to build libraries that have these constraints in size. And what stinks about that is then you have say, an older version of Lodash where you'd be like, “Okay, well it has 36 different functions in it and I'm only using 3 of them. And I have to ship them all to the browser.” CHARLES: Mmhmm. BEN: And that's not what you want. So, then we have these other solutions around tree-shaking and this and that. And the real thing is what you want is you want to be able to compose things left to right and you want to be able to have these functions that you can use on a particular type in an ad hoc way. And there's been two proposals to try to address this. One was the ‘function bind' operator, CHARLES: Mmhmm. BEN: Which is colon colon. And what that did is it said, “You can use this function as a method, as though it were a method on an object. And we'll make sure that the ‘this' inside that function comes from the instance that's on the left-hand side of colon colon.” CHARLES: Right. BEN: That had a bunch of other problems. Like there's some real debate I guess on how they would tie that down to a specific type. So, that kind of fell dead in the water even though it had made some traction. And then the pipeline operator is different. And then what it says is, “Okay, whatever is on the…” And what it looks like is a pipe and a greater than right next to each other. And whatever's on the left-hand side of that operand gets passed as the first argument to the function on the right-hand side of that operand. CHARLES: Mmhmm. BEN: And so, what that means is for the pipeable operators, instead of having to use a pipe method on observable, you can just say, “instance of observable, pipeline operator and an operator, and then pipeline operator, and then the Rx operator, and then pipeline operator and the Rx operator, and so on.” And it would just be built-in. And the reason I think that JavaScript really needs it is that means that libraries like Lodash can be written in terms of simple functions and shipped piece-meal to the browser exactly as you need them. And people would just use the pipeline operator to use them, instead of having to wrap something in a big object so you can dot-chain things together or come up with your own functional pipe thing like RxJS had to. CHARLES: Right. Because it seems it happens again and again, right? Lodash, RxJS, jQuery. You just see this pattern of chaining, which is, you know… BEN: Yeah, yeah. People want chaining. People want left to right composition. CHARLES: Mmhmm. BEN: And it's problematic in a world where you want to shake off as much unused garbage as possible. And the only way to get dot chaining is by augmenting a prototype. There's all sorts of weird problems that can come with that. And so, the functional programming approach is one method. But then people look at it and they say, “Ooh, yuck. I've got to wrap things in a function named pipe. Wouldn't it be nicer if there was just some syntax to do this?” And yeah, it would be nicer. But I have less control over that. CHARLES: Right. But the other alternative is to have right to left function composition. BEN: Right, yeah. CHARLES: But there's not any special syntax for that, either. BEN: Not very readable. CHARLES: Yeah. BEN: So, you just wrap everything. And the innermost call is the first one and then you wrap it in another function and you wrap that in another function, and so on. Yeah, that's not [inaudible]. But I will say that the pipe function itself is pretty simple. It's basically a function that takes a rest of arguments that are all functions. CHARLES: Mmhmm. BEN: And so, you have this array of functions and you just reduce over it and call them. Well, you return a function. So, it's a higher function. You return a function that takes an argument then you reduce over the functions that came in as arguments and you call each one of them with whatever result was from the previous. CHARLES: Right. Like Tracy mentioned in the pre-show, I'm an aspiring student of functional programming. So, would this be kind of like a monoid here where you're mashing all these functions together? Is your empty value? I'm just going to throw it out there. I don't know if it's true or not, but that's my conjecture. BEN: Yes. Technically, it's a monoid because it wouldn't work unless it was a monoid. Because monoids, I believe the category theory I think for monoid is that monoids can be concatenated because they definitely have an end. CHARLES: Right. BEN: So, you would not be able to reduce over all those functions and build something with that, like that, unless it was a monoid. So yeah, the fact that there's reduction involved is a cue that it's a monoid. CHARLES: Woohoo! Alright. [Laughter] CHARLES: Have you found yourself wanting to apply some of these more “rigorous” formalisms that you find out there in the development of RxJS or is that just really a secondary concern? BEN: It's a secondary concern. It's not something that I like. It's something I think about from time to time, when really, debating any kind of heavy issue, sometimes it's helpful. But when it comes to teaching anybody anything, honestly the Haskell-isms and category theory names, all they do is just confuse people. And if you tell somebody something is a functor, they're like, “What?” And if you just say it's mappable, they're like, “Oh, okay. I can map that.” CHARLES: [Laughs] Right, right. BEN: And then the purists would be like, “But they're not the same thing.” And I would be like, “But the world doesn't care. I'm sorry.” CHARLES: Yeah, yeah. I'm kind of experiencing this debate myself. I'm not quite sure which side I fall on, because on the one hand it is arbitrary. Functor is a weird name. But I wish the concept of mappable existed. It does, but I feel like it would be handy if people… because there's literally five things that are super handy, right? Like mappable, if we could have a name for monoid. But it's like, really, you just need to think in terms of these five constructs for 99% of the stuff that you do. And so, I always wonder, where does that line lie? And how… mappable, is that really more accessible than functor? Or is that only because I was exposed to the concept of mapping for 10 years before I ever heard the F word. BEN: Yes, and yes. I mean, that's… CHARLES: [Laughs] BEN: Things that are more accessible are usually more accessible because of some pre-given knowledge, right? What works in JavaScript probably isn't going to work in Haskell or Scala or something, right? CHARLES: Mmhmm. BEN: If someone's a Java developer, certain idioms might not make sense to them that come from the JavaScript world. CHARLES: Right. But if I was learning like a student, I would think mappable, I'd be thinking like, I would literally be thinking like Google Maps or something like that. I don't know. BEN: Right, right. I mean, look at C#. C#, a mapping function is always going to be called select, right, because that's C#. That's their idiom for the same thing. CHARLES: Select? BEN: Yeah. CHARLES: Really? BEN: Yeah, select. So, they'll… CHARLES: Which in Ruby is like find. BEN: Yeah. there's select and then, what's the other one, ‘select many' or something like that. [Chuckles] BEN: So, that's C#. CHARLES: Oh, like it's select from SQL. Okay. BEN: Yeah, I think that's kind of where it came from because people had link and then they had link to SQL and then they're like, well I want to do this with regular code, with just using some more… less nuanced expressions. So, I want to be able to do method calls and chain those together. And so, you end up with select functions. And I think that that exists even in Rx.NET, although I haven't used Rx.NET. CHARLES: Hmm, okay. ELRICK: So, I know you do a lot of training with Rx. What are some of the concepts that people struggle with initially? TRACY: I think when we're teaching RX Workshop, a lot of the people sort of… I'll even see senior level people struggle with explaining it, is the difference between observables and observers and then wrapping their head around the idea that, “Hey, observables are just functions in JavaScript.” So, they're always thinking observables are going to do something for you. Actually, it's not just in Angular but also in React, but whenever someone's having issues with their Rx applications, it's usually something that they're like nesting observables or they're not subscribing to something or they've sort of hot-messed themselves into a tangle. And I'm sure you've debugged a bunch of this stuff before. The first thing I always ask people is, “Have you subscribed?” Or maybe they're using an Angular… they're using pipes async but they're also calling ‘dot subscribe' on their observable. BEN: Yeah. So, like in Angular they'll do both. Yeah. There's that. I think that, yeah, that relates to the problem of people not understanding that observables are really just functions. I keep saying that over and over again and people really don't seem to take it to heart for whatever reason. [Chuckles] BEN: But you get an observable and when you're chaining all those operators together, you're making another observable or whatever, observables don't do anything until you subscribe to them. They do nothing. CHARLES: Shouldn't they be called like subscribable? BEN: Yes. [Chuckles] BEN: They probably should. But we do hand them an observer. So, you are observing something. But the point being is that they don't do anything at all until you subscribe to them. And in that regard, they're like functions, where functions don't do anything unless you call them. So, what ends up happening with an observable is you subscribe to it. You give it an observer, three callbacks which are then coerced into an observer. And it takes that observer and it hands it to the body of this observable definition and literally has an observer inside of there. And then you basically execute that function synchronously and do things, whatever those things are, to set up some sort of observation. Maybe you spin up a WebSocket and tie into some events on it and call next on the observer to get values out of your observable. The point being that if you subscribe to an observable twice, it's the same thing as calling a function twice. And for some reason, people have a hard time with that. They think, if I subscribe to the observable twice, I've only called the function once. CHARLES: I experienced this confusion. And I remember the first time that that… like, I was playing with observables and the first time I actually discovered that, that it was actually calling my… now what do you call the function that you pass to the constructor that actually does, that calls next or that gets passed the observer? TRACY: [Inaudible] BEN: I like to call it an initialization function or something. But the official name from the TC39 proposal is subscriber function. CHARLES: Subscriber function. So, like… BEN: Yeah. CHARLES: I definitely remember it was one of those [makes explosion sound] mind-blowing moments when I realized when I call my subscribe method, the entire observable got run from the very beginning. But my intuition was that this is an object. It's got some shared state, like it's this quasar that I'm now observing and I'm seeing the flashes of light coming off of it. But it's still the same object. You think of it as having yeah, not as a function. Okay. No one ever described it to me as just a function. But I think I can see it now. ELRICK: Yeah, me neither. CHARLES: But yeah, you think of it in the same way that most people think of objects, as like, “I have this object. I have a reference to it.” Let observable equal new observable. It's a single thing. It's a single identity. And so, that's the thing that I'm observing. It's not that I'm invoking this observable to observe things. And I think that's, yeah, that's a subtle nuance there. I wish I had taken y'all's course, I guess is what I'm saying. ELRICK: Yeah. BEN: Yeah. Well, I've done a few talks on it. CHARLES: [Laughs] BEN: I always try to tell people, “It's just a function. It's just a function.” I think what happens to a lot of people too is there's the fact that it's an object. But I think what it is, is people's familiarity with promises does this. Because promises are always multicast. They are always “hot”. And the reason for this is because they're eager. So, by the time you have a promise, whatever is producing value to the promise has already started. And that means that they're inherently a multicast. CHARLES: Right. BEN: So, people are used to that behavior of, I can ‘then' off of this promise and it always means one thing. And it's like, yeah, because the one thing has nothing to do with the promise. It wasn't [Chuckles] CHARLES: Right. BEN: This promise is just an interface for you to view something that happened in the past, where an observable is more low-level than that and more simple than that. It just states, “I'm a function that you call. I'm going to be able to do anything a function can do. And by the way, you're giving me an observer and I'm going to do some stuff with that too and notify you via this observer that you handed me.” Because of that you could take an observable and close over something that had already started. Say you had a WebSocket that was already running. You could create a new observable and just like any function, close over that, externally create a WebSocket. And then everyone that subscribes to that observable is tying an observer to that same WebSocket. Then you're multicast. Then you're “hot”. ELRICK: [Inaudible] CHARLES: Right. So, I was going to say that's the distinction that Jay was talking about. He was talking about we're going to just talk about… he said at the very beginning, “We're just going to talk about hot observable.” ELRICK: Yup. CHARLES: But even a hot observable is still theoretically evaluating every single time you subscribe. You're getting a new observable. You're evaluating that observable afresh each time. It just so happens that in the lexical scope of that observable subscriber function, there is this WebSocket? BEN: Yeah. So, it's the same thing. Imagine you wrote a function that when you called it created a new WebSocket and then… say, you wrote a new function that you gave an observer object to, right? An observer object has next, error, and complete. And in that function, when you called it, it created a new WebSocket and then it tied the ‘on message' and ‘on close' and whatever to your observer's next method and your observer's error message and so on. When you call that function, you would expect a new WebSocket to be created every single time. Now, let's just say alternately you create a WebSocket and then you write a new function that that function closes over that WebSocket. So, you reference the WebSocket that you externally created inside of your function. When you call that function, it's not going to create a new WebSocket every time. It's just closing over it, right? So, even though they both are basically doing the same thing, now the latter one of those two things is basically a hot observable and the former is a cold observable. Because one is multicast which is, “I'm sharing this one WebSocket with everybody,” and the other one is unicast which is, “I am going to create a new WebSocket for each person that calls me.” And that's the [inaudible] people have a hard time with. CHARLES: Right. But really, it's just a matter of scope. BEN: Yeah. The thing people have a hard time with, with observables, is not realizing that they're actually just functions. CHARLES: Yeah. I just think that maybe… see, when I hear things like multicast and unicast, that makes me think of shared state, whereas when you say it's just a matter of scope, well then I'm thinking more in terms of it being just a function. It just happens that this WebSocket was already [scoped]. BEN: Well, shared state is a matter of scope, right? CHARLES: Yes, it is. It is. Oh, sorry. Shared state associated with some object identity, right? BEN: Right. CHARLES: But again, again, it's just preconceptions, really. It's just me thinking that I've had to manage lists of listeners and have multicast observers and single-cast observers and having to manage those lists and call notify on all of them. And that's really not what's happening at all. BEN: Yeah. Well, I guess the real point is observables can have shared state or they could not have shared state. I think the most common version and the most composable version of them, they do not have any shared state. It's just one of those things where just like a function can have shared state or it could be pure, right? There's nothing wrong with either one of those two uses of a function. And there's nothing wrong with either one of those two uses of Observable. So, honest to god, that is the biggest stumbling block I think that I see people have. That and if I had to characterize it I would say fear and loathing over the number of operators. People are like… CHARLES: [Chuckles] BEN: And they really think because everyone's used to dealing with these frameworks where there's an idiomatic way to do everything, they think there's going to be an RxJS idiomatic way to do things. And that's just patently false. That's like saying there's an idiomatic way to use functions. There's not. Use it however it works. The end. It's not… CHARLES: Mmhmm, mmhmm. BEN: You don't have to use every operator in a specific way. You can use it however works for you and it's fine. ELRICK: I see that you guys are doing some fantastic work with your documentation. Was that part of RxJS 2.0 docs? TRACY: I was trying to inspire people to take on the docs initiative because I think when I was starting to learn RxJS I would get really frustrated with the docs. BEN: Yeah. TRACY: I think the docs are greatly documented but at the same time if you're not a senior developer who understands Rx already, then it's not really helpful. Because it provides more of a reference point that the guys can go back and look at, or girls. So anyways, after many attempts of trying to get somebody to lead the project I just decided to lead the project myself. [Laughter] TRACY: And try to get… the community is interesting because I think because the docs can be sometimes confusing… Brian Troncone created LearnRxJS.io. There's these other visualization projects like RxMarbles, RxViz, et cetera. And we just needed to stick everybody together. So, it's been a project that I think has been going on for the past two months or so. We have… it's just an Angular app so it's probably one of the most easiest projects to contribute to. I remember the first time I tried to contribute to the Ember docs. It literally took me an hour to sit there with a learning team, Ember Learning Team member and… actually, maybe it was two hours, just to figure out how the heck… like all the things I had to download to get my environment set up so that I could actually even contribute to the darn documentation. But with the Rx, the current RxJS docs right now is just an Angular app. You can pull it down. It's really easy. We even have people who are just working on accessibility, which is super cool, right? So, it's a very friendly place for beginners. BEN: I'm super pleased with all the people that have been working on that. Brian and everybody, especially on the accessibility front. Jen Luker [inaudible] came in and voluntarily… she's like the stopgap for all accessibility to make sure everything is accessible before we release. So, that's pretty exciting. TRACY: Yeah. ELRICK: Mmhmm. TRACY: So funny because when me and Jen started talking, she was talking about something and then I was like, “Oh my god, I'm so excited about the docs.” She's like, “I'm so excited, too! But I don't really know why I'm excited. But you're excited, so I'm excited. Why are you excited?” [Laughter] TRACY: I was like, “I don't know. But I'm excited, too!” [Chuckles] TRACY: And then all of a sudden we have accessibility. [Laughs] ELRICK: Mmhmm. Yeah, I saw some amazing screenshots. Has the new docs, have they been pushed up to the URL yet? TRACY: Nah, they are about to. We were… we want to do one more accessibility run-through before we publish it. And then we're going to document. We want to document the top 15 most viewed operators. But we should probably see that in the next two weeks or so, that the new docs will be… I mean, it'll say “Beta, beta, beta” all over everything. But actually also, some of our friends, [Dmitri] from [Valas] Software, he is working on the translation portion to make it really easy for people to translate the docs. CHARLES: Ah. TRACY: So, a lot of that came from the inspiration from the Vue.js docs. we're taking the versioning examples that Ember has done with their docs as inspiration to make sure that our versioning is really great. So, it's great that we can lend upon all the other amazing ideas in the industry. ELRICK: Oh, yeah. CHARLES: Yeah, it's fantastic. I can't wait to see them. ELRICK: Yeah, me neither. The screenshots look amazing. I was like, “Wow. These are some fabulous documentation that's going to be coming out.” I can't wait. TRACY: Yeah. Thank you. CHARLES: Setting the bar. ELRICK: Really high. [Laughter] CHARLES: Actually, I'm curious. Because observables are so low-level, is there some use of them that… what's the use of them that you found most surprising? Or, “Whoa, this was a crazy hack.” BEN: The weirdest use of observables, there's been quite a few odd ones. One of the ones that I did one time that is maybe in RxJS's wheelhouse, it was just that RxJS already existed. So, I didn't want to pull in another transducer library, was using RxJS as a transducer. Basically… in Netflix we had a situation where we had these huge, huge arrays of very large objects. And if you try to take something like that and then map it and then filter it and then map it and then filter it, we're using Array map and filter, what ends up happening is you create all sorts of intermediary arrays in-memory. And then garbage collection has to come through and clean that up. And that locks your thread. And over time, we were experiencing slowness with this app. And it would just build up until eventually it ground to a halt. And I used RxJS because it was an available tool there to wrap these arrays in an observable and then perform operations on them step-by-step, the same map, filter, and so on. But when you do that, it doesn't create intermediary arrays because it passes each value along step to step instead of producing an entire array and then doing another step and producing an entire array, and so on. So… CHARLES: So, will you just… BEN: It saved garbage collection and it increased the performance of the app. But that's just in an extreme case. I would never do that with just regular arrays. If anything, it was because it was huge, huge arrays of very large objects. CHARLES: So, you would create an observable our of the array and then just feed each element into the observable one at a time? BEN: Well, no. If you say ‘observable from' and you give it an array, that's basically what it does. CHARLES: Okay. BEN: It loops over the array and nexts those values out of the array synchronously. CHARLES: I see, I see. BEN: So, it's like having a for loop and then inside of that for loop saying, “Apply the map. Apply the filter,” whatever, to each value as they're going through. But when you look at it, if you had array map, filter, reduce, it's literally just taking the first step and saying ‘observable from' and wrapping that array and then the rest of it's still the same. CHARLES: Right. Yeah. No, that's really cool. BEN: That was a weirder use of it. I've heard tell of other things where people used observables to do audio synchronization, which is pretty interesting. Because you have to be very precise with audio synchronization. So, hooking into some of the Web Audio APIs and that sort of thing. That's pretty interesting. The WebSocket multiplexing is something I did at Netflix that's a little bit avant-garde for observable use because you essentially have an observable that is your WebSocket. And then you create another observable that closes over that observable and sends messages over the WebSocket for what you're subscribed to and not subscribed to. And it enables you to very easily retry connections and these sorts of things. I did a whole talk on that. That one's pretty weird. CHARLES: Yeah. Man, I [inaudible] to see that. BEN: But in the general use case, you click a button, you make an AJAX request, and then you get that back and maybe you make another AJAX request. Or like drag and drop and these sorts of things where you're coordinating multiple events together, is the general use case. The non-weird use case for RxJS. Tracy does weird stuff with RxJS though. [Laughter] CHARLES: Yeah, what's some weird uses of RxJS? TRACY: I think my favorite thing to do right now is to figure out how many different IoT-related things I can make work with RxJS. So, how many random things can I connect to an application using that? BEN: Tracy's projects are the best. They're so good. [Laughter] TRACY: Well, Ben and I created an application where you can take pictures of things using the Google Image API and it'll spit back a set of puns for you. So, you take a picture of a banana, it'll give you banana puns. Or you can talk to it using the speech recognition API. My latest thing is I really want to figure out how to… I haven't figured out if Bluetooth Low Energy is actually enabled on Google Home Minis. But I want to get my Google Home Mini to say ‘booty'. [Inaudible] [Laughter] CHARLES: RxJS to the rescue. [Laughter] BEN: Oh, there was, you remember Ng-Cruise. We did Ng-Cruise and on there, Alex Castillo brought… TRACY: Oh, that was so cool. BEN: All sorts of interesting… you could read your brain waves. Or there was another one that was, what is it, the Microsoft, that band put around your wrist that would sense what direction your arm was in and whether or not your hand was flexed. And people… TRACY: Yeah, so you could flip through things. BEN: Yeah. And people were using reactive programming with that to do things like grab a ball on the screen. Or you could concentrate on an image and see if it went blurry or not. ELRICK: Well, for like, Minority Report. BEN: Oh, yeah, yeah. Literally, watching a machine read your mind with observables. That was pretty cool. That's got to be the weirdest. TRACY: Yeah, or we had somebody play the piano while they were wearing one of the brainwave… it's called the OpenBCI project is what it is. And what you can do is you can actually get the instructions to 3D print out your own headset and then buy the technology that allows you to read brain waves. And so with that, it's like… I mean, it was really awesome to watch her play the piano and just see how her brain waves were going super crazy. But there's also these really cool… I don't know if you guys have heard of Jewelbots, but they're these programmable friendship bracelets that are just little Arduino devices that light up. I have two of them. I haven't even opened them. CHARLES: [Laughs] TRACY: I've been waiting to play with them with you. I don't know what we're going to do, but I just want to send you lights. Flashing lights. [Laughter] TRACY: Morse code ask you questions about RxJS while you're working. [Laughter] CHARLES: Yeah. Critical bug. Toot-toot-toot-too-too-too-too-toot-toot. [Laughter] CHARLES: RxJS Justice League. TRACY: That would actually be really fun. [Laughter] TRACY: That would be really fun. I actually really want to do that. But… CHARLES: I'm sure the next time we talk, you will have. TRACY: [Laughs] Yes. Yes, yes, yes, I know. I know. we'll do it soon. We just need to find some time while we're not going crazy with conferences and stuff like that. CHARLES: So, before we head out, is there any upcoming events, talks, releases, anything that we ought to be, we or the listeners, ought to be aware of? TRACY: Yeah, so one of the things is that Ben and I this weekend actually just recorded the latest version of RX Workshop. So, if you want to learn all about the latest, latest, newest new, you can go ahead and take that course. We go through a lot of different things like multiplex WebSockets, building an application. Everywhere from the fundamentals to the more real world implementations of RxJS. BEN: Yeah. Even in the fundamentals area, we've had friends of ours that are definitely seasoned Rx veterans come to the workshop. And most of them ask the most questions while talking about the fundamentals. Because I tend to dig into, either deep into the internals or into the why's and how's thing. Why and how things work. Even when it comes to how to subscribe to an observable. Deep detailed information about what happens if you don't provide an error handler and certain cases and how that's going to change in upcoming versions, and why that's changing in upcoming versions, and what the TC39's thoughts are on that, and so on and so forth. So, I try to get into some deeper stuff and we have a lot of fun. And we tend to be a little goofier at the workshops from time to time than we were in this podcast. Tracy and I get silly when we're together. TRACY: It's very true. [Laughter] TRACY: But I think also, soon I think there are people that are going to be championing an Observable proposal on what [inaudible]. So, aside from the TC39 Observable proposal that's currently still at stage one, I don't know Ben if you want to talk a little bit about that. BEN: Oh, yeah. So, I've been involved in conversations with folks from Netflix and Google as well, Chrome team and TC39 members, about getting the WHATWG, the ‘what wig', they're a standards body similar to W3C, to include observables as part of the DOM. The post has not been made yet. But the post is going to be made soon as long as everybody's okay with it. And what it boils down to is the idea of using observables as part of event targets. An event target is the API we're all familiar with for ‘add event listener', ‘remove event listener'. So, pretty much anywhere you'd see those methods, there might also someday be an on method that would return an observable of events. So, it's really, really interesting thing because it would bring at least the primitives of reactive programming to the browser. And at the very least it would provide maybe a nicer API for people to subscribe to events coming from different DOM elements. Because ‘add event listener' and ‘remove event listener' are a little unergonomic at times, right? CHARLES: Yeah. They're the worst. BEN: Yeah. CHARLES: That's a very polite way of putting it. BEN: [Chuckles] So, that's one thing that's coming down the pipe. Other things, RxJS 6 is in the works. We recently tied off 5.5 in a stable branch. And master is now our alpha that we're working on. So, there's going to be a lot of refactoring and changes there, trying to make the library smaller and smaller. And trying to eliminate some of the footprints that maybe people had in previous versions. So, moving things around so people aren't importing stuff that were meant to be implementation details, reducing the size of the library, trying to eliminate some bloat, that sort of thing. I'm pretty excited about that. But that's going to be in alpha ongoing for a while. And then hopefully we'll be able to move into beta mid first quarter next year. And then when that'll be out of beta, who knows? It all depends on how well people like the beta and the alpha, right? CHARLES: Alright. Well, so if folks do want to follow up with y'all either in regards to the course or to upcoming releases or any of the other great stuff that's coming along, how would they get in touch with y'all? TRACY: You can find me on Twitter @ladyleet. But Ben is @BenLesh. RX Workshop is RXWorkshop.com. I think in January we're going to be doing state of JavaScript under This Dot Media again. So, that's where all the core contributors of different frameworks and libraries come together. So, we'll definitely be giving a state of RxJS at that time. And next year also Contributor Days will be happening. So, if you go to ContributorDays.com you can see the previous RxJS Contributor Days and figure out how to get involved. So, we're always open and happy and willing to teach everybody. And again, if you want to get involved it doesn't matter whether you have little experience or lots of experience. We are always willing to show you how you can play. BEN: Yeah. You can always find us on Twitter. And don't forget that if you don't find Tracy or I on Twitter, you can always message Jay Phelps on Twitter. That's important. @_JayPhelps. Really. TRACY: Yeah. [Laughter] BEN: You'll find us. CHARLES: [Chuckles] Look for Jay in the show notes. [Laughter] CHARLES: Alright. Well, thank you so much for all the stuff that y'all do, code and otherwise. And thank you so much Ben, thank you so much Tracy, for coming on the show. BEN: Thank you. CHARLES: Bye Elrick and bye everybody. If you want to reach out to us, you can always get in touch with us at @TheFrontside or send us an email at contact@frontside.io. Alright everybody, we'll see you next week.

Conal Elliott, Target, USA United States, gives the third presentation in the second panel, Functional Programming Techniques, in the ICFP 2017 conference. Parallel programming, whether imperative or functional, has long focused on arrays as the central data type. Meanwhile, typed functional programming has explored a variety of data types, including lists and various forms of trees. Generic functional programming decomposes these data types into a small set of fundamental building blocks: sum, product, composition, and their associated identities. Definitions over these few fundamental type constructions then automatically assemble into algorithms for an infinite set of data types--some familiar and some new. This paper presents generic functional formulations for two important and well-known classes of parallel algorithms: parallel scan (generalized prefix sum) and Fast Fourier Transform (FFT). Notably, arrays play no role in these formulations. Consequent benefits include a simpler and more compositional style, much use of common algebraic patterns--such as Functor, Applicative, Foldable, and Traversable--and freedom from possibility of run-time indexing errors. The functional generic style also clearly reveals deep commonality among what otherwise appears to be quite different algorithms. Instantiating the generic formulations to "top-down" and "bottom-up" trees as well as "bushes", two well-known algorithms for each of parallel scan and FFT naturally emerge, as well as two possibly new algorithms.

Julie Moronuki: @argumatronic | argumatronic.com Show Notes: 00:57 - Julie's Unique Origin Story Into Programming 03:47 - Good Resources vs Bad Resources for Learning Haskell 11:18 - Areas to Look at Before Taking on Haskell and Functional Programming 15:56 - Terminology 17:50 - The Haskell Pyramid 25:51 - Learning Haskell Vocabulary 28:20 - Monoid and Functor 42:06 - Advice for Someone Who May Not Be Interested in Programming Resources: Haskell Programming From First Principles (Haskell Book) Natural Language Processing (NLP) Learn You a Haskell for Great Good! Programming in Haskell by Graham Hutton Haskell: The Craft of Functional Programming by Simon Thompson Real World Haskell by Bryan O'Sullivan, John Goerzen, and Don Stewart Introduction to Functional Programming Course with Eric Meijer The Joy of Haskell Haskell eXchange 2017 - A Monoid For All Seasons Transcript: CHARLES: Hello everybody and welcome to The Frontside Podcast, Episode 83. My name is Charles Lowell, a developer here at the Frontside and your podcast host-in-training. With me today on the podcast is Elrick also. Hello Elrick. ELRICK: Hello. How you doing? CHARLES: I'm doing well. I'm glad to have you on this one. I'm glad to be doing this podcast in general. We have someone on the podcast today who I've been following for, I guess probably about two years because she published a book that has been very, very helpful to me. It's one that I recommend to a lot of people. It is learning Haskell from first principles. With us on the show is Julie Moronuki, who is co-author of that book. Thank you so much, Julie for coming. JULIE: Yes, hi! Happy to be here. It's nice to finally get to talk to you. CHARLES: Yeah. One of the reasons I wanted to have you on the podcast was because I feel as though you have one of the most unique origin stories because of programming and entering in the tech world. Most of us are curious, we either come from video games or maybe we just start fiddling with the web browser. You enter the maze from the entrance that is like hidden from all, I would say. You went straight to writing a book on Haskell, is that --? JULIE: That is what happened. In 2014 on Twitter, I met my co-author, Chris Allen and he has been trying to figure out better ways to teach people Haskell because the on-ramping, I guess of people to Haskell can be quite difficult. The materials that exist are not always accessible and people felt like they need the advanced math degrees before they can write Haskell. He was trying to figure out better ways to introduce people to it. Since I was this person who's never programmed before -- I have no background -- and then he thought, "This will be a very different experience, trying to teach Haskell to her." Because I have a linguistics background and stuff he thought, "That would be interesting too and maybe, she'd be interested eventually in doing NLP." I said, I'm not -- CHARLES: What's that? Acronym alert. JULIE: Oh, yeah. Sorry. Natural Language Processing. I said, "You know, I've never done any programming and I don't play video games and I never have had any desire to learn computer programming. I don't think I'm going to like this. I don't think this is going to last but sure, I will try," and so I did a little bit. I read a little bit of 'Learn You a Haskell for Great Good.' I've read some other things. CHARLES: This was before you guys had the idea of actually writing a book. JULIE: Yes. He had the idea of turning some of his thoughts about teaching Haskell into a book and as he would explain things to me, like the questions I had about 'Learn You a Haskell,' I'd be like, "We should write this down," and he would say, "It's so hard to write it though. It's easy when I'm explaining it to you and it's so hard to write it." Initially, it started that I was helping him at things that he was teaching me and then as we got further into the book and I started reading a lot of other Haskell stuff on my own and figuring stuff out, I was writing more and more of it. Then we were kind of equal co-authors after not too long. That's how it happened. I really didn't think that I would stick with Haskell or with programming. I'm still sometimes I'm not sure about programming. I'm not sure about this whole making software thing. But Haskell is so interesting to me that I'm still here. CHARLES: That is fantastic and it's a great story. I'm curious, when you were doing the proto-research to learning Haskell, coming from really truly first principles and having no experience of programming, what made a good resource versus a bad resource? What are the things that you gravitated towards and say, "This is really instructive." What was the tone there? JULIE: One of the major problems ahead of most of the Haskell resources that exist is they assume that you've done programming before because nobody learns Haskell as a first language so they all assume that you have done some programming before. They would make references to things that if you were a programmer, you would know what they meant but I didn't. That was one of the hardest things for me. Even 'Learn You a Haskell' does that to some extent. CHARLES: What's an example of that? JULIE: I had learned a little bit about recursion from linguistics because that's a thing in human language so I really understood recursion but most of the Haskell resources explain it to you primarily in terms of, "This will be like your loops in other languages." I'm going to be like, "I don't know what a loop is. This isn't helpful for me." There are a lot of things that I didn't understand so when people talk about Haskell as being a pure functional language, neither pure nor functional necessarily, I didn't have anything to contrast them with so they didn't necessarily make sense to me as things that make Haskell different from other languages. I didn't know what imperative programming was and people would say, "In contrast to imperative programming, functional programming does this," and I'd be like, "Okay, but I don't understand what the imperative programming way is so this contrast isn't making any sense to me and same thing with purity." There were a lot of things I had to learn, in fact about mutable state because I didn't know anything about it. I had some understanding of how computer memory works but still some of the ways that people talk about it were not obvious to me. CHARLES: Do you find that seeking out that contrast actually wasn't helpful? Is it noise since at least at the beginning, it's something you'll never do. It's like saying, "Over in France, they wear these kind of socks." Since I'm going out into the street in front of my house, I don't really care. JULIE: Right. In the beginning, it was a lot of noise and I understand why they do that because they are making the assumption that everybody who is learning Haskell has come from some other programming language, probably an imperative one so I understand why that happens but in the beginning, it was very much noise for me. I noticed a lot of Haskell resources, one of the first things they tell you is that in Haskell you can't do 'x = x + 1'. I was like, "If I'm reading this like it's mathematics, why would I think I could do that." If you come from a different programming language, you might well think that you can do that but in Haskell, we can't so making that contrast, when I didn't have that background was really just confusing for me. Now, because I teach people and most of them do have some background in an imperative language, understanding the contrast is more helpful to me but in the beginning it was just confusing and noise. When we wrote Haskell book, we tried not to make those kinds of references and like, "Let's assume that everybody is just like Julie, doesn't know a different programming language that we can contrast it with and let's try to write a book like that." CHARLES: Right. I think that's a key insight because some people would say there's a lot missing or that difference might stand out. Now, that you pointed out, I can see it but I don't think I noticed it while I was reading it. But one of the things that I like is because I also tried to learn Haskell through 'Learn You a Haskell,' and I didn't find it very helpful. I found it entertaining and it's not a knock against the authors. Some of the sketches were really cute but it was still more explaining... I don't know. It was explaining more of the how, than the why, if that makes any sense where I felt as though in your book, there were a lot more analogies to actual human experiences, using the visceral language saying, "A mono is something you can mash together or squeezed together." That really connected for me. Whereas, explaining it in terms of concatenation and laws and stuff like that. Those things seem cited to the secondary resources to the primary resource. JULIE: Yeah. I think that's kind of helpful for me too. There are different Haskell books that have, I think different things about them that are good. I forget the name of the book but Graham Hutton's book, the way he talks about recursion was really helpful to me. The way he explains recursion and of course, folds but folds are things that he's known for so those parts of that book are helpful for me. But really the best book other than my own of course, for me is Simon Thompson's. I think it's called ‘The Craft of Functional Programming' and I think it does better at explaining things just in terms of Haskell. Real World Haskell, I guess is really good. It was harder for me because I hadn't been a programmer before. I think it's got so many practical exercises that -- CHARLES: Was that the O'Reilly book by Irish gentleman whose name eludes me? JULIE: Yes, Brian O'Sullivan. It makes more sense to me now but there were things in it that are sort of programmer things. Because I'd never made software before, that were really confusing for me. But Simon Thompson's, because his book does have exercises and they were ones that I could understand and do. They were fairly self-contained. My first experience actually in writing a program that does IO was from his book and I was just so thrilled. I was like, "I got it. I did it." That was really helpful book for me but I don't see people recommend that one as often but that was probably the best one for me. CHARLES: Yeah, it's always a balance because the Real World Haskell didn't really worked for me, almost because the examples were too pragmatic or too complex and I picked this up when I was 10 years into my programming career and I struggled to follow the JSON parser example, which is parsing JSON is something that I've actually done several times in multiple languages and I still struggled with it. JULIE: Whereas for me, I don't even know what JSON is. This is not something I've ever dealt with. I know what it is now sort of, but it's still not something that I deal with very much. I was just like, "What is this? I don't even know what to do here." It wasn't quite as helpful for me. I've heard a lot of people have success with that one but I think they don't share quite the same richness of programming experience with Brian O'Sullivan. I think it's a little bit more difficult. ELRICK: These are a lot of amazing resources that I wish I knew about when I try to learn Haskell. I took an online course with, I think it's like Eric Meijer and that class was very intense. Looking back, what would you say are some areas that someone should, either start to look into before they step into the Haskell world, being that you didn't come from a programming background but connecting to dots backwards now? What would you say are some areas that people can slowly ramp up into to get into Haskell and functional programming? JULIE: When I teach people Haskell, the people who have the easiest time are people who have been writing Scala for a while and they've moved over to the FP in Scala side. When I first started Haskell, I heard a lot of people make jokes about how Scala is a gateway drug to Haskell. I think there's actually might be so truth in that because I certainly have a lot of students that were Java programmers, then they got interested in Scala because maybe Scala is better for some things than Java and then they start moving more and more over to the FP in Scala side. Those are probably the students that have, I think the easiest time making the transition to Haskell that I've had anyway. But you know, I think even JavaScript, trying to write in a more functional style and there are some resources for that and really, there's a very good tutorial about monads that uses all the code examples in JavaScript. I think a lot of the concepts that you can start to approach them from other languages. Haskell is still going to be weird in a lot of ways and another thing that works for a lot of people is going to Elm. Elm is similar to Haskell but different. I think that that has worked also for a lot of people getting them into understanding more functional programming concepts but with the much easier... The word easy is so -- ELRICK: It's like a relative term like, "Oh, this is easy." JULIE: It is. CHARLES: Easy to say, right. ELRICK: That's what I thought when I step into learning Haskell and functional programming. I was like, "How bad could it be?" JULIE: Right. Learning Haskell can be very bad. I'm not going to kid around about that. It's a shame because I don't think that it needs to be that bad but the way it's presented oftentimes, for various reasons, I think why Haskell gets presented the way it does but I don't think it needs to have it like that. The designer of Elm, whose name I'm not going to try to pronounce because I don't know how you say his last name, he really made an effort to for example, the error messages in Haskell can be very intimidating. The situation there has improved since I started learning Haskell but they can be quite intimidating and he really made an effort to make very friendly error messages, very helpful error messages. I think that it shows and then it makes a difference for people who are learning. If you start with Elm and then you do want to see what Haskell or PureScript, which is also frontend language, mostly. It compose of JavaScript but it's very Haskell-like, then from Elm, let's see if we can get a little more hardcore Haskell. I think the transition to Haskell or PureScript is easier from there. I think it does help to move in the functional direction from whatever language you're in, if you do FP in Scala or try moving to more functional JavaScript or even Elm. Then Haskell will make it more sense from there or be a little easier to approach. CHARLES: Yeah, and I definitely think that for, at least from my perspective, I've been able to take a lot of those concepts that I've learned from Haskell and then apply them, even inside Vanilla JavaScript. There are things that have become indispensable like mapping and folding and they exist in JavaScript. You can reduce arrays, which is a similar to a fold and then you can map arrays but understanding that map, the key insight for me that I got from learning Haskell is that there's a whole class of values that you can map, not just arrays. The standard JavaScript object is essentially a Functor and will get a little bit to that because for people listening what that word even means and the meta around the fact that they're all these weird words and how do I go about something I want to ask you about. But the trees can be mapped and the objects can be mapped and all of the sudden, it's like this one concept that I use so much for lists, it's available on all these different data structures and it's get me thinking like, "What other data structures can I use this operation? What are the things are Functors that I'm working with?" Really, it's changed my perspective to think about the type of the data structure, in terms of the operations. JULIE: I'm in favor of keeping the terminology that we have but just explaining it much better. That's the approach that I take but it can be very hard, especially it was your first learning Haskell. I don't know if you've seen the Haskell pyramid but to get sort of productive where you can write programs in Haskell is not a very high bar. It feels like it is when you first start but it's not really very high bar but Haskell just keeps growing and growing and getting deeper and deeper so you're always approaching new libraries that you've never seen before and you feel then you've been learning Haskell all over again because they're written in a very different style of Haskell or they have even more terminology, even more kinds of Functors that you've never heard of before or something like that so you're always approaching these things over again. It can be a very intimidating feeling and it makes a lot of people very uncomfortable and I'd say, if you like Haskell and that does make you feel uncomfortable, then you don't actually need to do that because a lot of people write Haskell very happily every day in their jobs even and don't do that. They don't mess with some of the newer, super cool libraries that have all this funky terminology and stuff. Some of them don't mess with them at all. CHARLES: But certainly, there is some concepts that are core. I'm thinking of like applicative and Functor and all these things that I'm learning about and I'm curious to hear about your experience as you climb that pyramid. What is the pyramid entailed? First of all, I'd love to hear more about it because this is actually the first time I heard about the Haskell pyramid. JULIE: Say you understand monads, then you can write really a lot of Haskell programs. Probably at some point, you will need to understand monads transformers but if you just get to the point where you understand monads pretty decently, you can write a lot of software so after that, then learning more is maybe going to improve your Haskell, maybe let you write some things that you couldn't write before but a lot of it above, not that these things are necessarily in an hierarchical progression. We cover monad transformers in a fair bit of detail in Haskell book but if you get anything beyond what's in Haskell book, one of those things that some of them are very interesting, some of them can make you much more productive but some of them are also people do them for fun to explore the space and some people love them and some people hate them. Haskell lets you do a lot of things for fun and exploring mathematics in ways that are interesting and exciting and may influence and in fact, have influenced other languages like [inaudible] in PureScript but not really necessary for basic Haskell programming. A nice thing happened while we're writing Haskell book. I was writing, I think it's chapter six, which is about type classes. I was writing that chapter and at the same time, my co-author had started writing the Monoid chapter. The type classes chapter comes in chapter six and we introduce a lot of the basic type classes: num and eq and some of those in that chapter because I do think it's important. Type classes are very special thing about Haskell so I think it's important to, at least start coming to groups at them early. Some people disagree with me about that and think they can ignore them for much longer. But at any rate, it is where it is and I felt that that was important. Maybe the real motivation for type classes, really until we started writing the Monoid chapter so he started writing that while I was working on type classes chapter and he sent me the beginnings of the Monoid chapter to look at. At first I thought, "We've got addition and multiplication and list concatenation and this just doesn't seem interesting. What is this generalization of a Monoid that I'm supposed to get from these three things? And why bother making it a type class," because additional and multiplication are already in the num type class and then list concatenation is just for list so why make this into a type class and what's that motivation there. With eq, we want a quality -- CHARLES: Is that how you pronounce 'eq?' JULIE: That's how I pronounce it because 'equal' or equality. CHARLES: Okay, so this is a type class for doing what? Making sure to being able to compare two values on the same value. JULIE: Yes and it's a weird one because for most data types, you can have an eq instance and you want probably, in a lot of cases to have that but we don't want because function is a data type in Haskell so you don't want to have an eq instance for functions and that's why equality is not implemented generally for everything. That's why it's a type class so there's no instance for functions because that's not decidable. You can't decide if two functions are equal, generally. Some functions you can but in the general terms, for datatype, you can't. CHARLES: That's actually a pretty profound statement. Proof of which is left as an exercise for the listener. JULIE: We got to the Monoid and I was like, "What is the [inaudible]," or something. It turns out that there are Monoids everywhere. There's all kinds of things that you want to, either concatenate or make a product of. Then having this as a type class and thinking of it in terms of like, "We've got this abstraction. We've got this category. We've got this algebraic structure. Now, we can look for in all these other places," because once you've named the thing, then you can talk about it and think about it in a little bit of the different way. It's like, "Now, we've got this group of addition, multiplication, list concatenation." Now, we've got an abstraction of that and we can think, "Where else can I see this pattern?" and it turns out it's all over the place. For me, that was one of our thought like, "Type classes are actually really cool and powerful and interesting thing." For me, that was when it seemed like, "The terminology is worth it because, now I want to think about finding these algebraic structures and in all these other places." CHARLES: Right and like a Monoid, it could essentially be called, if you're using a Java interface, like 'mashable togetherable' or 'concatenatable' or something like that. But there's a kind of one-to-one correspondence but it is a vocabulary that just needs to be learned. JULIE: I don't know much about category theory or anything but the other cool thing about Monoid for me was that there are almost always two because there's almost always one that's destructive or additive or concatenative and there's almost always one that is conjunctive or a product or multiplicative. It's often across product that would be the zipless Monoid that exist in base and it's a cross product of the two lists. There's almost always two, whereas when you think of Monoids in the very abstract looking category theory, it doesn't matter if it's addition or multiplication. The operation doesn't matter, whether it's addition or multiplication or concatenation or cross product because you generalize the actual operation to the extent where what it's going to produce. It doesn't matter anymore. For me, I still think of Monoids in terms of like set theory or Boolean Algebra, then that's one of the things that I think is difficult with Haskell where people talk about Monoids in terms of category theory but I think that's not very helpful for the actual programmer who has to actually deal with the two different instances like sum and products or concatenation and zipping are going to actually act different in a program. CHARLES: Right, they're going to yield a different set of values. JULIE: Yes. CHARLES: Is there a baseline vocabulary? I kind of think of it like learning a new language, right? JULIE: Yep. CHARLES: When you're learning Haskell, you're not just learning a new language. You're literally learning a new language. I could go and I could learn Japanese but it's going to be a struggle at some point. People say certain languages are hard and certain language are easy. I don't generally subscribe to that. I think that most of it is just going about and living in a place where they speak this language and you'll absorb it and it's the decision to go and live there -- that's kind of the primary one. But let's say, you're a foreigner and you're travelling to this country called Haskell that's got this strange language. Like other human languages, it's just got different names associated with different concepts and some of the concepts might even just be unique to that country. Just like when you're travelling and acquiring a human language, there's a certain level of vocabulary that you need to achieve before you can do things like buy groceries and be able to transact financial exchanges or have a conversation about the weather. What are the kind of the levels of vocabulary that you need to acquire to be operational in Haskell or I would say, even in functional programming because now that I've been exposed to this, I see it in Clojure. I actually see people doing this JavaScript and in Erlang, in Elixir and what have you. JULIE: Yeah, I don't really know how to answer this question. How to buy groceries in Haskell? CHARLES: Let me let scale that down because I had this horrible tendency to spend five minutes asking what I say is going to be single question but it's actually like 30. Let's take down the scope. When you were learning this vocabulary, at what point did you feel like you're really gaining traction? We're you really starting to connect the dots? JULIE: For me, I think when I got through Functor. It was when I felt like -- CHARLES: Functor and what comes before Functor? JULIE: Monoid. I think once you understand Monoid and Functor, then a lot of other concepts in Haskell will start falling into place because this is not obvious to everyone but I think once you really understand Monoid and once you really understand Functor, then applicatives are monoidal Functors and that's not obvious to everyone. Like I said, it's not obvious at first certainly, and monads have characteristics of both Monoid and Functor as well. Then you start saying, "There's all these other Functors. There's profunctors and bifunctors. I think once you really understand Monoid and Functor, a lot of the rest of Haskell starts falling into place and then type classes like alternative. Alternative is another kind of Monoid. We have all these other names that if you can see the general pattern of Monoids and Functors, I think to me anyway, a lot of it then just started falling into place. Applicatives to me seemed, I don't want to say obvious or simple but in traverse, it's same sort of thing so we have these other names for it -- traversable -- and I was like, "Why was it called traverse. I don't understand this word at all." But once I saw the type signature and what actually happens with what the function traverse does, I was like, "Okay, I see what's happening here." For me, those were the two big hills. Once I got through Monoid and Functor and really understood them well, then a lot of other stuff just come and fell into place for me. ELRICK: This is really interesting. How was a Monoid explained to you when you were first starting to learn Haskell? Then now, how do you explain what a Monoid is to someone that's learning Haskell? JULIE: When Monoid was first explained to me, it was the pattern of there's addition and multiplication and list concatenation so it generalize out that pattern and that was really hard for me to understand at first because list concatenation and addition are similar but multiplication is different. I was like, "What do these three things have in common?" What they have in common is that they take two values of a certain type and return another value of that type and that's the type signature of the main function, that's in the Monoid type class. But that doesn't really tell you very much. A lot of functions could do that, in theory at least. How you combine them is really what's interesting about Monoid and also what makes concatenation and addition different from multiplication. Fortunately in college, I had had a fair bit of exposure to Boolean Algebra so figuring out that like, "There's actually two basic genres or varieties of Monoid and they are disjunctive or additive or they are conjunctive or multiplicative," and figuring that out, to me I always think that Monoid should really be, maybe two different type classes, one for the additive Monoid like list concatenation and addition and things where you are adding two things like a set union. Then conjunctive, which would be this intersections or multiplication or cross products. I always think there's maybe should be two different type classes but there's not a good way to do that really in Haskell. Instead, we have this one type class and then we do this ugly business of wrapping them in different type names. CHARLES: Is that why you'll have a constructor for some so it's just a wrapper for an integer? JULIE: Yeah. CHARLES: I don't know if that's so bad. JULIE: I don't like it but -- CHARLES: Yeah. You know what? You do a lot more than I do so I'm going to take your word for it. JULIE: Yeah, that's exactly why. Sum and product are the wrappers for integers because integer doesn't have a Monoid. It has two Monoids over it. CHARLES: I see. There's lots of ways to combine integers. JULIE: Yeah and those are the two basic ones. Then because Monoids also have an identity so with semi-groups, then you get even more semi-groups for integers because you get max and min, because they don't have an identity so there's semi-groups. CHARLES: There's always risk getting down into the weeds with the vocabulary but I think that there's a message here because your answer to the question is really, "When I understood Monoid and I understood Functor," from that point on, the overhead that you had to expend to get other things was lower than the overhead that you had to expend to get those initial two things. For anyone listening, Monoid and Functor are probably opaque terms. You have no idea what the hell they mean. We've been talking about in things like that a little bit but then it's okay because they're a finite set of opaque terms and they're very achievable and once you can achieve those, then you've done 90% of the work and now, you're just combining them into interesting and novel ways. JULIE: Yes. I will say it that a lot of people do tell us about Haskell book that applicative is actually the hardest chapter in the book, not monad but applicative. CHARLES: Really? JULIE: Yeah. A lot of people do tell us that. Because that's the first time that you've taken the concept of Monoid and the concept of Functor and combining them into a new thing so then, once you've done that with applicative, then after that, really it's all downhill. CHARLES: Right. It seems like there's a couple of key insights. As you're climbing that hill, I like that analogy is like one, just understanding that there things like type classes so you've through attacking Monoid and through attacking Functor, you realize, "There is such a thing." By recognizing there is such a thing as a Functor, you recognize that there is the potential for other type classes like it. Then through combining it with Monoid, to get applicative, you can see, "I can actually compose these things into new instances of those things," and then that's either the crest of the hill or the Pandora's box, depending on which way you look at it. I think there's a hopeful message in there that if you can invest the time to learn these opaque terms and making them transparent to you, you can really, really, really lean heavily on that knowledge in going forward. JULIE: Yeah. I'm writing a new book now called 'The Joy of Haskell.' The idea of The Joy of Haskell is meant to be an intermediate book. For people who already know some Haskell but we want to make words like Functor more general, like in Haskell book we really focused on the type class called Functor when it's actually a concept from mathematics or actually originally from linguistics oddly enough but we really focused on the type class in there, rather than trying to explain what a Functors are generally. In the new book, in The Joy of Haskell, we're going to try to take a lot of these terms like Monoids and Functors and catamorphisms and all these other words that Haskell has used all the time and try to explain them generally. Then also give examples like interesting uses from different libraries and stuff like that. It'll service both, hopefully a guide to the vocabulary of the Haskell ecosystem and also some documentation and examples for libraries and things like that that are useful because these things do have uses. They do get used in interesting and exciting or terrifying -- maybe those are related -- ways. That's the goal of the new book is to try to make a guide to all of this vocabulary that Haskell use all the time. We're trying to do that. How do I explain Monoids, you asked. You've got two values of whatever type. It doesn't matter the type and in general, there would be two ways you can think of to combine them, either making a sum or a union of all the values in them or making some product of those values, if they contain multiple values or even if they only contain one. That's how I explain them now. I'm not certain that addition and multiplication are actually the best ways to start with that because addition and multiplication don't act quite like set union and intersection do. I'm actually thinking of them in terms of and this is how I explain monoids to the people now, I start from set theory and that sounds really heavy but it doesn't have to be because I think a lot of things about sets are -- CHARLES: They're very intuitive, especially if you have visuals. JULIE: They're very intuitive, for people to think about. Yes, exactly. I explain Monoid now more in terms of set union and intersection. I'm actually giving a talk in October. It's coming up in just a couple weeks at Haskell eXchange in October 12th and 13th in London and I'm giving a talk there called 'A Monoid For All Seasons' and I'm going to try to explain the theoretic motivation for Monoids and try to explain them in those terms. Semi-group is a little bit different because lacks the identity but I'll try to explain the alternative type class and monad plus this really the same thing as alternative. These things are also just Monoids so we have these different names because it's a different type class alternative but it's really just another kind of Monoid. I'm giving that talk about set theory in Monoids in October, in a couple of weeks. People keep asking me on Twitter, "What's your obsession with Monoids," because my name on Twitter is Monoid Mary so I try to explain why I love them so much. CHARLES: Actually, it's an awesome point, which I've just gotten to experience it is what you see like, "Oh, there are these abstract things," you start searching for them. A lot of times, you'll uncover them and it'd be a real timesaver. There's the thrill of unearthing it in the first place and then when you could say, "Now that I've identified this thing as a Monoid, there's so much less that I have to write." There's like less work that I have to do. It's the same reason that we write frameworks for ourselves in software. It's like, "We love Ruby on Rails because of all the work we don't have to do." Now, you have to expend a lot of energy to work with it, using Rails an example but there's lots of software frameworks. It's like, "If you can find a good persistence framework or you can find a good thing for making a library for handling HTTP requests and responses, why would you write it all by hand in the first place?" I think the thing that's exciting for me as a developer is being able to see, "Monoid is a thing. Functor is a thing and I can now actually use this and I can use it almost as a looking glass to explore the world around me. When I see something in the landscape that just leaps out through that lens is another great one." I've been on a big kick lately but being able to say, "This is going to save me so much time because of the thoughts that I don't have to think and the code that I don't have to write." I think connecting it back to the pragmatic, I certainly have become really obsessed, maybe not about Monoids but having a type class large in your mind. JULIE: I think it's a really powerful thing. Sometimes that jargon is really useful. It's useful in a sense that it like compresses a bunch of information into a single word to remember. It's like teaching my eight-year old multiplication and we were talking about like, "It's like addition," and for us adult, I'll just go ahead say, "It's associative and commutative," but showing him that you can do those things and that addition is like that too and we're talking about that and he was so excited to learn that there's this word 'commutative' that encapsulates this idea for both concepts so he doesn't have to think like, "Addition does this thing. Multiplication does this thing." He doesn't have to remember both of those things, like he just remembers, "Commutative and they're both like this." It kind of compresses that information and what you have to remember and think about. Then it does make it easier to see that pattern in other things, then we can find commutativity in other things because now we have this pattern that we can look for and we got a name for it. We can talk about it and really, there's a lot of stuff like that in Haskell where we find some pattern that we find useful or we want to be able to talk about or easily translate to a bunch of different types, not translate is quite the right word but you know what I mean, I think. Then we give it a name and we make type class for it and then it's, "Now, we find it even more place for us." CHARLES: Right. It's about thinking less, right? JULIE: Yeah. CHARLES: That's a big misconception is that it's not about thinking more, it's about thinking less. JULIE: It really is. I think it's because there's so much kind of upfront work, where you have to learn all this new stuff upfront, then people mistake that for how much work we're always doing but in Haskell it's like, "We did all this work upfront and now we're now we're not going to think about these things anymore." ELRICK: That sounds like a good title for a book, 'Learn Haskell and you will think less," but it's true. When I struggled through that online class, I came out of that just being able to pick up any functional programming language and just hit the ground running. It is definitely a plus and you will think less. JULIE: Yeah, in the long term, I think that you do. Haskell is not a perfect language. There are things that probably can be improved. CHARLES: Now, before we go, I wanted to ask you, having had this very unique on-ramp into programming, which apparently you're still not convinced about. I'm curious what it would take to actually convince you but the real question that I have is there any advice that you have for someone who does not have a stereotypical background in programming who may not think that they would find programming interesting, who might have any number of roadblocks in terms of their own conceptions about the path forward. What advice would you have for them? JULIE: I am a bit joking when I say that I'm still not sure about writing software. I don't feel like I'm good at it and I think this is really the key. There are a bunch of domains in programming that I don't personally care about. I don't want to make web apps and I have nothing but respect and admiration for people who do. To me, it's very, very hard. CHARLES: Mostly because our tools aren't the same. JULIE: Yeah and there's just so many things outside your own program, there are just so many things that you have to think about and deal with because there's the network and there's other people's computers and they might be doing in other people software and what it might be doing. It is insane so for me it's very hard. There's a lot of domains of programming that I don't care about and when I thought about programming, that's the kind of thing I would think about. I certainly knew a lot of people who are web developers or the common programming jobs, I guess. Some of them just weren't that appealing to me and I'm not interested in making games or graphics so those are the kinds of things that I thought about for programming. There are things though that I am interested in doing. I'm very interested in natural language processing and I guess that's related to machine learning. I've recently taken up an interest in things like the raft protocol, the consensus protocol. Those kinds of things interest me a lot and there's a lot of the theory that interests me. I'm reading a dissertation right now about implementing a non-strict lambda calculus, which is what Haskell is. It's a non-strict lambda calculus and this guy's dissertations are theoretically implementing a non-strict lambda calculus. To me, the theoretical side is really interesting but then I am also interested in certain kinds of software. For some reason, I have developed quite an interest in making Twitter bots. I think that the advice I would give -- I'm rambling a little bit -- to people who think they're not interested in programming so why should they learn or whatever, is just find the thing that you are interested in and there's probably a way you can make software for that and maybe that will be the thing that will get you interested. It might not be Haskell, maybe you are interested in making web apps, in which case I would say go for Elm or PureScript, obviously because I like functional programs but Haskell might not be the best first language for you in that case but find the thing that you're interested in and there probably is a way to write software to do that. There's probably something in programming that will interest you. It's such a vast field. CHARLES: All right. I really, really like that answer. ELRICK: Yeah, that's a beautiful advice. Find your domain. CHARLES: Yeah, it's bigger than you think. JULIE: It's much bigger than you think. CHARLES: And there is a place for you. Thank you so much for coming on the show, Julie. I really, really, really enjoyed our conversation. JULIE: Yes, so did I. This is a lot of fun. CHARLES: Thank you. Now, before we go, I understand that you are going to be in London, was it roughly very, very soon, you said you were giving a talk. JULIE: Yes, the 12th and 13th of October. It will be recorded for people who can't get in. It will be recorded, I believe. CHARLES: You will be talking on 'A Monoid For All Seasons.' JULIE: Yes. CHARLES: And then you've also got The Joy of Haskell book, which you're hacking away right now, right? JULIE: Yes. CHARLES: With that, thank you so much for both of you. Thank you all for listening. What's a good place for people to reach out for you? JULIE: If they're on Twitter, I'm very active on Twitter so I'm @argumatronic on Twitter and my blog is also Argumatronic and that has more contact information. CHARLES: Fantastic. We'll link to those in the show notes. For everybody else, thank you for listening. You can get in contact with us at @TheFrontside on Twitter and Contact@Frontside.io over email. We'd love to hear from you. This just in, we're running a special. If you go to our website and enter the promo code 'ELRICK20,' you can get that 20% discount on your next custom developed web application. Go check that out. Take it easy, everybody. Bye-bye. JULIE: Bye-bye.

Building on the power of functors we examine a few scenarios where a normal Functor is problematic. Fortunately, there is a closely related structure known as an Applicative Functor that can provide the capabilities to solve a broader range of problems. Episode 17 patrons: Chad Wooley David Keathley Andre Carvalho Show Notes: Coconut programming language: http://coconut-lang.org/ Hack nights instead of presentations: http://tech.noredink.com/post/142283641812/designing-meetups-to-build-better-communities class Functor f => Applicative f where pure :: Applicative f => a -> f a ap :: Applicative f => f (a -> b) -> f a -> f b Example of applicative usage: pure (+) Just 3 Just 2 -- this results in Just 5 (+) Just 3 Just 2 -- this is the same as above liftA2 (+) (Just 3) (Just 2) -- alternate form using lift instead of infix operators

Новости: Релиз Akka 2.5.0 Причины неудачных релизов Scala 2.11 (раз, два) ScalaMeta 1.7.0 with scala js support Eventuate 0.9 sbt 0.13.15 effects4s Видеозаписи со Scala Matsuri Видеозаписи со ScalaSphere Интересная livecoding сессия как практическое введение в Functor, Applicative, Monad и Free Monad на примере Scalaz Playing "Type Tetris" Темы: Introduction to programming with dependent types in Scala Полезняшки: lightbend-emoji typesafe-emojr Building and Running Modern Data-Driven Apps on DC/OS drone-dynamic-agents hammock hedgehogqa akka-stream-kafka-template.g8 Голоса выпуска: Вадим Челышов, Евгений Токарев, Алексей Фомкин, Дмитро Митин

Your favorite features of Type Systems in one episode! Interfaces, Generics, ADT, Type Classes and Dependent Types. We'll talk about what they are and how they shape the way we work. Code Podcast Forum: https://discuss.codepodcast.com/t/episode-5-type-systems/22 Episode produced by: Andrey Salomatin https://twitter.com/flpvsk Michael Beschastnov michael@codepodcast.com Guests (in order of appearance): Joseph Abrahamson https://twitter.com/sdbo Radoslav Kirov https://twitter.com/radokirov Erlend Hamberg https://twitter.com/ehamberg Edwin Brady https://twitter.com/edwinbrady Special thanks to our reviewers, this time: Adriano Melo https://twitter.com/AdrianoMelo Roman Liutikov https://twitter.com/roman01la If you'd like to help us make the podcast better *and* get episodes earlier, consider becoming a reviewer: https://gist.github.com/filipovskii/f12685bc74a425ba651c736fb5e3e5ae ## Links: Basics Benjamin C. Pierce "Types and Programming Languages" https://www.cis.upenn.edu/~bcpierce/tapl/ A draft of the book available for free: http://ropas.snu.ac.kr/~kwang/520/pierce_book.pdf Rob Nederpelt and Herman Geuvers "Type Theory and formal proof" http://www.win.tue.nl/~wsinrpn/book_type_theory.htm Robert Harper "Practical Foundations for Programming Languages" https://www.cs.cmu.edu/~rwh/pfpl.html Interview with Jesper Louis Andersen about Erlang, Haskell, OCaml, Go, Idris, the JVM, software and protocol design — PART I https://notamonadtutorial.com/interview-with-jesper-louis-andersen-about-erlang-haskell-ocaml-go-idris-the-jvm-software-and-b0de06440fbd#.rawqi9bvp Paper by Xavier Leroy "Manifest Types, Modules, and Separate Compilation" (1994) http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.14.3950 Paper by Conor McBride and Ross Paterson "FUNCTIONAL PEARL: Applicative programming with effects" http://strictlypositive.org/IdiomLite.pdf ## Links: Idris Edwin Brady "Type-Driven Development with Idris" http://tinyurl.com/typedd ## Links: TypeScript http://www.typescriptlang.org/ ## Links: Haskell Christopher Allen and Julie Moronuki "Haskell Programming from First Principles" http://haskellbook.com/ Learn you some Haskell http://learnyouahaskell.com/ ## Links: Scala Paul Chiusano and Rúnar Bjarnason "Functional Programming in Scala" https://www.manning.com/books/functional-programming-in-scala ##Links: OCaml Yaron Minsky, Anil Madhavapeddy, Jason Hickey "Real World Ocaml" https://realworldocaml.org A chapter from "Real World Ocaml" about Objects https://realworldocaml.org/v1/en/html/objects.html OCaml Documentation http://caml.inria.fr/pub/docs/manual-ocaml/ Effective ML (video) https://blogs.janestreet.com/effective-ml-video/ ## Links: Discussions What exactly makes the Haskell type system so revered (vs say, Java)? http://softwareengineering.stackexchange.com/questions/279316/what-exactly-makes-the-haskell-type-system-so-revered-vs-say-java What is a Functor? http://stackoverflow.com/questions/2030863/in-functional-programming-what-is-a-functor#2031421 ADTs vs Inheritance http://stackoverflow.com/questions/3271974/why-adts-are-good-and-inheritance-is-bad Existential vs Universal Typess http://stackoverflow.com/questions/14299638/existential-vs-universally-quantified-types-in-haskell#14299983 Subclassing vs Subtyping http://www.cs.princeton.edu/courses/archive/fall98/cs441/mainus/node12.html Why Haskell has no subtyping https://www.reddit.com/r/haskell/comments/423o0c/why_no_subtypingsubtype_polymorphism/ Haskell vs Java type systems http://softwareengineering.stackexchange.com/questions/279316/what-exactly-makes-the-haskell-type-system-so-revered-vs-say-java ## Music Mid-Air! @mid_air

Functional programming has a lot of concepts which have to be yet discovered by mainstream programming. One, known especially from the Haskell programming language, are Lenses. Johannes Thönes met Chris Ford, Software Developer and ThoughtWorker from London, during XConf in Hamburg where he gave a talk on implementing Lenses in Clojure. In this 23 minute interview, Johannes talks with Chris about his experience with Lenses in Clojure. First they define what a Lense is and what you would want to do with it. Then they talk about the specifics of implementing Lenses in a programming language introducing the terms Functor and Function. We close the episode by talking about the possibility to implement lenses in other programming languages such as Java 8 or JavaScript.