Episode 35 - Functional Programming with C# with Simon Painter

In this episode we will dive into functional programming , but before we get started , I want to remind you to follow us on social media so you never miss an episode , and it helps us to reach more amazing people like yourself . Today we have a special guest called Simon Painter . Could you please introduce yourself ?

I started working in NET 2 , and I've worked in pretty much every version of NET that's ever been , and these days , of course , I'm big into functional programming , amongst other things , and that's what I'm here to talk about today .

in your day job ?

And they make software for use by recruiters . So it's stuff like candidate tracking , like upload a CV , track them through the process , make comments , evaluate , do , give evaluation quizzes out to your candidate and then aggregate together a short list of the best candidates all that sort of a thing .

Arrange interviews all the sorts of things you do when you're trying to hire new staff . So that's what we do , Thankfully and rather conveniently for me . They're actually a functional programming house . That is the style that they write all of their code to , which is handy for me .

So it meant that , rather than have a lengthy period of learning what functional programming is as I come on board , I didn't need to do any of that because I sort of literally wrote a book on the subject once and it meant that I could just get straight on with a little bit . There was some in-house style to learn , but get .

Get straight on with a little bit . There was some in-house style to learn , but get more straight on with the coding when I started . So I think that was a relief to them in some ways , although they have had to put up with all of my terrible , terrible jokes in meetings .

Then Does that mean all the rest doesn't work ? It's a terrible name . It's a bit like organic food or what's all the rest of the food ? Is it inorganic rocks and stuff ? No , it's called functional programming because everything's made of functions .

Everything in functional programming is made of functions and it's functions which are sort of plugged together like Lego bricks . You know , if you imagine a Lego brick as being a small little function , you could place many Lego bricks together to make a larger , more complex function and then to a larger , more complex system .

But the whole thing is composed of many little functions glued together . This is actually something that's been in NET in principle since about C-sharp 3 . Link is based on functional programming . If you think about link , when you call a select , what you were doing is those arrow expressions , those arrow functions you write . Those are functions .

Those are little , tiny functions which are being passed into another function as a parameter and then executed by that function in a certain context , which is it , takes it and then runs it against every element in an enumerable . That's a basic functional programming concept Functions passed around as if they were variables and functions called by other functions .

By doing that , by passing a function into a select statement , you are composing two functions together to make a larger , more complicated behavior .

yeah , absolutely , that is definitely a . There's no state as such in functional programming . So OOP is predicated

on the idea that you have this big blobby state object , for example , and then your program runs and updates state . It updates this object , it pulls data from it , pushes data to it . We don't have a state object in functional . We kind of have this state as a concept , but it's more like state is a transitory continuity of objects .

Um , which one sec , excuse me , sorry , which um ? Which exists only for a moment .

And um , what you do to update state is , instead of literally updating the object , you you take the old state object some parameters , some little bits of data and an instruction and create a new state object based on the old one , which may sound on the face of it a little overly complicated , but it gives you this advantage of incredibly predictable state

management systems . You get code that is and that's the really big one You're writing a code base which is really , really predictable . Everything is written with a principle in mind . We can call it pure functions or something like that .

The idea is , every function that you write is written in such a way that it will always return the same data given the same parameter values . That is , the same parameter values . So if you're adding an add function , you give it a 10 and a 20 , always giving it back a 30 every single time , and nothing else .

It involves eliminating the concept of side effects . Side effects are things like throwing unhandled exceptions or , um , skipping to other bits of the code base any other way , uh , or updating something that isn't contained within the function itself .

Once you get rid of all those side effects , all of your code becomes really very predictable , which makes it easy to do things like writing unit tests or to immediately . You don't have to worry about things like side effects happening when you're running , say , a whole load of processes in parallel .

You tend not to get things like resource contention happening in cases like where you're doing multiprocessing on data with lots of different tasks running all in parallel . It tends to handle those sorts of scenarios really really well . So Azure Functions , stuff like that that tends to be supported by functional programming .

To some extent it predates the modern concept of the computer . The first functional programming language was made in the late 50s . It was called Lisp , written by a guy called John McCarthy . So functional programming has been around absolutely ages and for almost any given programming language I guarantee you that you write programming language in functional programming .

You'll probably find there's already a book on this subject or several Python for example . I'm almost certain that book exists . I think I've seen it around C++ , javascript certainly JavaScript supports functional programming very , very well , better than most programming languages do .

Just by the sort of fluid nature of JavaScript it can be everything and everything to everyone , except when it isn't because it's JavaScript and occasionally it's an empty array or something . But JavaScript does functional very , very , very well indeed . And Java , of course . Java and C Sharp are remarkably similar to each other .

be I won't mention Batch , because Batch is not a programming language . It could be like JavaScript and Python and stuff .

When I got my very first job in the early 2000s , I was actually trained as a Java developer . That was when I did my degree at university . Actually , the languages I learned at university were Java and C++ and C of all things . C is still very useful and very important , but most of us don't work in it , and those were languages I studied at university .

But as soon as I got my first professional job , they wanted me to work in C Sharp , but I'd never seen it before . But I had done Java and of course they're very transferable .

I do know Python as well . As it happens , I run a code club in my kids' school and I teach them Python Python because we use the code club material that's codecluborg and that's largely Python-driven and Python's both open source and a scripting language , so it's handy for teaching the kids .

There's rules here about who's allowed to attend which school , usually based on where you live . So it's actually the school that my children attend and both of my kids are members of the club as well . Um , so it's , it's run well .

It's on break at the moment because there's some exams and they are being worked on and we're coming to the end of the school year , but it generally runs on a monday and , uh , it's runs for an hour or so after school . I teach them a bit of Python . I try and give them a bit of context about how does the wider world of computing work .

I try and teach them what it is like in the computing industry and what's the truth about the sort of rubbish that films teach you about how computers work , when that's not quite how the real world is , especially hacker films I have a love-hate relationship with hacker films and how accurately and not they portray .

I did ask my brother , who is a school teacher , what would be a lovely way to motivate the kids . Like you know , I thought being a school teacher himself , he would know all of this sort of stuff . And it turned out to be stickers , just give them stickers yeah .

There was one of the early ones where you have to make a rocket to make it fly up into space and you have some readouts that tell you how much fuel it's burned and whether your rocket made it to space .

That's cool little stuff and , to be honest , one of the most rewarding moments for me is often when one of the kids just starts and they write their first hello world . And would you believe , like I mean , I've been working in some form , either as a student or as a professional , in programming since 1996 .

And I have long forgotten the joy of the Hello World . It's so rewarding just to see kids excited because they made their computer write something .

Now my book is published by O'Reilly , enrico Buonanno's is published by Manning , and I think we're both pretty good books , but either of those would be a very good place to start . I have numerous talks that I've given on the subject which are available on youtube , if that's of any interest to anyone .

I also do workshops , if anyone's company wants to , to bring some of these benefits in . I'm sure that , uh , I'm sure they can reach out to me and we can have a discussion . Yeah , there's plenty of material out there , plenty no worries , uh , so I'll .

joining this podcast , simon . So we learned about some functional programming , so I hope everyone knows some bit of functional programming . It's quite useful and it's how everything can be built and from in functional and yeah so thanks for joining . So let's , just before we end the podcast , we just want to just want to know a bit more about yourself .

So I said what I see you're like an mvp , so are you doing any community activities , like doing any talk or events , like you mentioned ?

Um , I've been doing that for about 10 years I think now , and I also attend international conferences and I give talks . I was at ndc oslo recently and I was at um tecarama in belgium , in antwerp , and I give talks at them as well and as of now , I do workshops as well . So , yeah , I do a lot of public speaking .

Um , I started at community conferences in the UK events like DDD East Anglia was my very first one and stuff like that . I've kind of worked my way up to uh , to attending some slightly bigger conferences , but I still attend , uh , all of the community conferences and community events around the UK .

At least any of them have me and they're within travel distance of me , because I love speaking at these things . I really enjoy getting out and traveling and meeting people and talking about all of this yeah , there's a difference between like speaking than actual just blogging .

podcast , are you going to any other events ? And you said you got user groups talk next week where ?

Um , I , in september I am going to be going to ndc copenhagen where I'll be once again talking on all manner of things . I I don't have much else planned after that , but I have applied for .

I will also be appearing at b sides in um in leeds . Uh , that's actually I'm going to be talking security there . That's one of my other . That's one of my other topics I talk about . That's a security talk .

It's next Monday , I think Next Monday yeah , so the details will be on like a meetup is net north , so just google it on the meetupcom and you just need to register it . Okay , thank you bye .