Right-to-left argument application?

[philbooth]

This is probably a terrible idea, but how do you feel about using the << operator to support applying arguments from right-to-left? People would need to parenthesise if they were mixing both operators in one statement (or to keep it simple you could prohibit mixed usage entirely).

In other words:

bar(123) << foo;
// Compiles to bar(foo, 123);

[adlawson]

Transcript from our Skype conversation so I don't forget what we said:

Andrew Lawson: I was thinking about using some sort of placeholder to do it, like

foo >> bar(*, 123)

Andrew Lawson: dunno
Phil Booth: ah, cool, that would be much cleaner
Phil Booth: my << idea felt like a complete can of worms as i was writing it down
Andrew Lawson: I dunno, I do quite like your way though
Andrew Lawson: I'll try them both out :)
Phil Booth: the thing is, if you're scanning code quickly, i suspect yours will stand out more
Phil Booth: less errors from misreading
Phil Booth: also, there is plenty scope for some horrific statements if people had a need to mix both
Andrew Lawson: yeah, I see what you mean
Andrew Lawson: I'll try them both out anyway and see what happens

[adlawson]

Again, taking pointers from Elixir, I'll likely use the & character by default to reference the input.

foo >> bar(&, 123); // bar(foo, 123);
foo >> bar(123, &); // bar(123, foo);

// Without reference, pushes it onto the end
foo >> bar(123); // bar(123, foo);

I think if it's implemented like this it makes sense to make it possible to add the reference to the middle of the partial.

foo >> bar(1, &, 2, 3); // bar(1, foo, 2, 3);
foo >> bar(1, 2, &, 3); // bar(1, 2, foo, 3);

[philbooth]

Oh yeah, that's heaps better! :)