Discussion on: JS Functional Concepts: Pipe and Compose

[Mwenedata Apotre]

I just knew pipe and now I know it differs to compose by just order of function execution! Thanks

[JoelBonetR 🥇]

Anytime 😁

[Douglas Massolari]

That's not always true, though.
In Elm, for example, pipe |> and composition >> have the same order of execution, the difference is that pipe is imediately executed while composition returns a new function:
Note: Everything after -- is a comment in Elm

add x y =
  x + y

sub y x =
  x - y

totalWithPipe =
  1
    |> add 10
    |> sub 5 -- 6

totalWithComposition =
  let
    calculateTotal =
      add 10 >> sub 5 -- returns a function
  in
  calculateTotal 1 -- 6

Not only in Elm, but pipe in fp-ts also works this way:

import { pipe } from 'fp-ts/function'

const len = (s: string): number => s.length
const double = (n: number): number => n * 2

// without pipe
assert.strictEqual(double(len('aaa')), 6)

// with pipe
assert.strictEqual(pipe('aaa', len, double), 6)

[JoelBonetR 🥇]

That's why the post has the tag #javascript 😁, either way love the insight! I haven't coded in Elm in ages, actually a good one, absolutely love the no runtime errors 🤩

It's sad that it got relatively few support...

[Douglas Massolari]

Yes, but even in Javascript this concept can be different as you can see in fp-ts’ pipe.

I love coding in Elm! It is my first option when creating a Frontend.

From what I see, it seems some companies are adopting it, so, it seems it’s growing

[JoelBonetR 🥇]

I picked the mathematical explanation for function composition:

In abstract algebra, a composite function is a function formed by the composition or successive application of more than one function. To do this, the function closest to the argument is applied to the argument, and the next function is applied to the result of the previous calculation.

in which case, this will fit in the description:

compose(function3, function2, function1)(initialArg);

The implementation details or nuances in Elm (or any other) is a different matter of discussion 😁

BTW glad to hear Elm it's getting a bit more love!

[Douglas Massolari]

You are right.
But the point of my comment is pipe.
This is the one that have different implementations.
I just highlighted that the affirmation “pipe is the same as composition but reversed” is not always true

[JoelBonetR 🥇]

oh! understood now 😁 my bad