Comma-based syntax

[ivan7237d]

It's a simple idea, so probably came up before in some discussion and was rejected, but since I couldn't find it discussed after searching through all the issues, let me bring it up here.

The idea is that instead of x |> a |> b |> c, the syntax would be x |> a, b, c. There are two reasons behind this syntax:

• As with ponyfills like applyPipe(arg, f1, f2, f3), you will not have to put arrow functions in parens. Precedence-wise, a => b |> c would mean a => (b |> c). a |> b => c, d can only mean a |> (b => c), d.

• Sometimes it's convenient to compose functions without applying them. Right now you can do this with a function like pipe(f1, f2, ...), and it's conceivable that in future there would be a separate JS operator for that. Either way, preferably it should be easy to move function chains back and forth between usages in function composition, and usages with pipeline operator. When these chains uniformly use the comma as the separator, this is taken care of.

I suspect there are some footguns or other flaws here, but the only one I see right away is that one could confuse the commas for the comma operator. A comma already has special meaning in contexts like let a, b though.

[ljharb]

That meaning is still “a list of expressions” since variable declarations are expressions.

it would be very strange if the expression a, b, c meant something different inside a pipeline than outside it.

[ivan7237d]

it would be very strange if the expression a, b, c meant something different inside a pipeline than outside it.

There's an interesting comment by @masaeedu, #96 (comment), pointing out that in the current proposal, |> already means different things depending on whether it occurs in the RHS of another |>.

[charmander]

@ivan7237d That was a misunderstanding based on reading it with the wrong associativity.

[tabatkins]

Closing this issue, as the proposal has advanced to stage 2 with Hack-style syntax.