Constant stack usage

[gabejohnson]

The current proposal desugars

"hello"
  |> doubleSay
  |> capitalize
  |> exclaim;

to

exclaim(capitalize(doubleSay("hello")));

If I want to reuse this pipeline I can write

const sayItAgainLouder = s => s |> doubleSay |> capitalize |> exclaim;

Now I get reuse, but I'm allocating three stack frames. This isn't a big deal unless I want to compose sayItAgainLouder with some other functions.

A simple alternative desugaring

[doubleSay, capitalize, exclaim].reduce((value, f) => f(value), "hello");

This decreases stack usage, but I imagine at the cost of speed.

It would be useful if this proposal required the compiler to maintain constant stack usage through either some sort of stream fusion or stack frame reuse.

[jasmith79]

I don't think that's within the intended uses: if you want to compose pipelines you'll be using compose rather than an infix operator. Ditto for long chains using lots of stack space: if your pipeline is ridiculously long then it should probably be built up using compose in pieces rather than one long chain that fills more than your text editor can display.

[gabejohnson]

if you want to compose pipelines you'll be using compose rather than an infix operator.

I might agree with you @jasmith79 if there was a builtin compose that guaranteed constant stack usage.

I'm all for a built-in though. See fantasyland/ECMAScript-proposals#1

Ditto for long chains using lots of stack space: if your pipeline is ridiculously long then it should probably be built up using compose in pieces rather than one long chain that fills more than your text editor can display.

I haven't suggested this usage. I did mention composing functions with other composed functions.

[dtinth]

If I understand correctly,

exclaim(capitalize(doubleSay("hello")))

works like

let _tmp = "hello"
_tmp = doubleSay(_tmp)
_tmp = capitalize(_tmp)
_tmp = exclaim(_tmp)
_tmp

Therefore there is no nested stack frame?

[gabejohnson]

@dtinth you're right. For some reason I was thinking the behavior was the same as how some pipe functions are implemented resulting in something like

(x => exclaim((x => capitalize((x => doubleSay(x))(x)))(x)))('hello')

which

exclaim(capitalize(doubleSay("hello")))

does not.

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