changes in iterators

[igotfr]

whl (cond) {}

itr (e <- a) {}

instead for (e in a)
for would be used only as c-like for
in would be used to check if an element is in a collection, for instance:

2 in [1, 2, 3]

for (let i: u8 = 0; i < a.len; i++) {}

[lexi-nadia]

C-style for-loops are complex to read and write, especially in cases where the index isn't just an integer. That's why Carbon (and Swift, Go, Kotlin, Rust...) use for for logical iteration. Any C-style for-loop can be easily expressed as a while loop, and the result is less "magic" (it's more obvious when each line is executed):

let i: u8 = 0;
while (i < a.len) {
  ...
  i++;
}

But also, this type of loop should be a lot less common in Carbon than in C++, due to things like slices.

[igotfr]

C-style for-loops are complex to read and write, especially in cases where the index isn't just an integer. That's why Carbon (and Swift, Go, Kotlin, Rust...) use for for logical iteration. Any C-style for-loop can be easily expressed as a while loop, and the result is less "magic" (it's more obvious when each line is executed):

let i: u8 = 0;
while (i < a.len) {
  ...
  i++;
}

But also, this type of loop should be a lot less common in Carbon than in C++, due to things like slices.

Carbon may not have C-style for, even so, itr is more idiomatic
Rust uses the macro matches! instead in, just because in is reserved for use in for, <- would solve it

[lexi-nadia]

Please feel free to write up a formal proposal and send it for comment. :)

[tkoeppe]

Please also see #471, which proposed some concrete details of loops, but was deferred due to the general lack of an overall loop design.