Partial Application: Stage 1

[jamiebuilds]

Champion: @rbuckton
Repo: https://github.com/rbuckton/proposal-partial-application
Slides: https://docs.google.com/presentation/d/1GSnqtT1jHbilIAwCuaK2yjKNj0y6cLfJNisZDig3Nm8/edit?usp=sharing
First presented at the Sept 2017 meeting

Example

const addOne = add(1, ?); // apply from the left
addOne(2); // 3

const addTen = add(?, 10); // apply from the right
addTen(2); // 12

// with pipeline
let newScore = player.score
  |> add(7, ?)
  |> clamp(0, 100, ?); // shallow stack, the pipe to `clamp` is the same frame as the pipe to `add`.

const maxGreaterThanZero = Math.max(0, ...);
maxGreaterThanZero(1, 2); // 2
maxGreaterThanZero(-1, -2); // 0

Syntax

f(x, ?)           // partial application from left
f(x, ...)         // partial application from left with rest
f(?, x)           // partial application from right
f(..., x)         // partial application from right with rest
f(?, x, ?)        // partial application for any arg
f(..., x, ...)    // partial application for any arg with rest

[jamiebuilds]

Note that there were a number of concerns about the syntax in the Sept 2017 meeting. Particularly with how these are too similar:

fn(...b); // spread args, calls fn
fn(...,b); // placeholder, does not call fn

It was asked that there be a different syntax which is applied towards the start of a call:

<HERE>foo<OR_HERE>(x++)

But it was also raised that ... adds more complexity than it may be worth.

[ljharb]

Additionally, a number of members raised concerns that it might not ever be possible for the syntax to be made viable to make it to stage 2.

[rajasekarm]

I'll pick this.

[byara]

Hi, I would like to work on this. One thing, I'm going to learn a lot, the other, I'm writing my Bachelor thesis about Babel compiler so doing something for Babel would mean a lot.