"Truthy pipe" syntax proposition

[akx]

For a lark, I wanted to see what some Django ORM code might look like in Coco and ended up with

object-list =
  Category.objects.language instance.language
  |> if category = instance.category then &filter {category} else &
  |> &slice instance.count

-- this works alright, but the second line of the chain is kinda ugly because of the else branch.

So I'd propose a "truthy pipe" syntax, perhaps ?>, so any falsy values in that block would be emitted as & instead.

object-list =
  Category.objects.language instance.language
  ?> (&filter {category} if category = instance.category)
  |> &slice instance.count

Currently, with Coco 0.9, with |> instead of ?> the following JS is emitted (I've added some linebreaks for readability), and obviously the "void 8" emitted as the implicit "else" breaks the chaining.

var objectList, x$, category;
objectList = (
  x$ = Category.objects.language(instance.language),
  x$ = (category = instance.category) ?
    x$.filter({category: category}) :
    void 8,
  x$.slice(instance.count)
);

In addition I wouldn't mind it if ?> had a slightly different precedence so the parentheses in the post-if wouldn't be necessary...

[satyr]

A new operator solely for omitting at most 7 bytes in a narrow situation sounds overkill.

[satyr]

Closing for the reason above.

I wouldn't mind it if ?> had a slightly different precedence so the parentheses in the post-if wouldn't be necessary...

As for this issue, |> is given the lowest precedence present (as I didn't want to create yet another level) which happens to be the same as post-if. May have been a mistake considering expressions like a |> b if c |> d unintuitively evaluates as ((a |> b) if c) |> d.

[vendethiel]

On a single line, isn't it going to conflict with post-if specialcase ?

[satyr]

What specialcase exactly?

[vendethiel]

I'm talking about inline implicit object rule (something like that), 140c648.

[satyr]

The brace-insertion for implicit objects kicks in before the parser job. They may seem to interact oddly, but not in a conflicting way.

[vendethiel]

I don't really get what happens in cases like a |> b c: d |> foo if bar.

[satyr]

It goes:

a |> b {c: d |> foo} if bar

↓

a |> b({c: d |> foo}) if bar

↓

a |> (b({c: d |> foo}) if bar)

Hm. Probably |> should also close inline implicit objects.

[vendethiel]

Yeah, that's what I thought.