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Functional programming in C++, Python, etc.

Nahiyan Alamgir on November 25, 2018

Let's say I want to print to the screen. In pure functional programming languages like Haskell or Elm, you can simply leave it to the runtime engin...
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rhymes •

Regarding Python...

I think you already know the answer: you can't...

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Nahiyan Alamgir •

You're right, we can't have have 100% pure functional code. The idea is to keep as much of the core pure functional while the rest has to remain imperative.

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Muhammed H. Alkan •

Actually, you can. What are the reasons to can't functional in Python?

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rhymes •

You can do a bit of functional programming: docs.python.org/3.7/howto/function...

It's just that it's not a functional language per se. It was designed as a general purpose, multi paradigm, language.

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Muhammed H. Alkan •

So basically you're meaning all of the multi paradigm languages has no paradigm, so like Scala is not functional nor object oriented. Sorry but that's a little bit absurd. You just have to obey the rules, nothing else. Functional programming doesn't mean purely functional programming. It's not hard at all functional programming in Python.

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rhymes •

No, I was saying exactly the opposite 😅

You can mix object orientation and functional programming.

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Evgeny Pogrebnyak •

Check out docs.python.org/3/howto/functional... (as mentioned). For "pure function which prints text on the screen" I think you are stuck, unless you review what is your defintion of fucntional.

If you are to encapsulate your output into IO monad in python you can try github.com/dbrattli/OSlash, but this is just an excercise. 

from oslash import put_line, get_line

main = put_line("What is your name?") | (lambda _:
    get_line() | (lambda name:
    put_line("What is your age?") | (lambda _:
    get_line() | (lambda age:
    put_line("Hello " + name + "!") | (lambda _:
    put_line("You are " + age + " years old"))))))

if __name__ == "__main__":
    main()

I thing more fruitful concepts in functional programming are curring, map/filter/reduce and function composition.

Regarding the nice code in gist.github.com/nahiyan/4ea3181b6b... - I think you are just mimicing one behaviour of bind as concat string, while binding can perform different actions on container content. Also there is a difference on class type and an OOP class, as discussed for example here stackoverflow.com/questions/270465....