Sorry, I love Rust but I can’t really agree with you here. They only showed a macro_rules!definition, which is definitely rust syntax. Lifetime annotations are relatively common.
I will concede that loop labels are incredibly rare though.
I guess I see what you mean if we want to get very technical about what a syntax extension is. But I think for the purpose of this discussion, it’s reasonable to think of macro_rules! as a part of the Rust language. Practically speaking, it is syntax provided by the language team, not just users of the language who are free to extend the syntax by usingmacro_rules! to do so.
Loop labels are rare, but they lead to much simpler/clearer code when you need them. Consider how you would implement this kind of loop in a language without loop variables:
'outer: while (...) {
'inner: while (...) {
if (...) {
// this breaks out of the outer loop, not just the inner loopbreak'outer;
}
}
// some code here
}
In C/C++ you’d need to do something like
bool condition = false;
while (...) {
while (...) {
if (...) {
condition = true;
break;
}
}
if (condition) {
break;
}
// some code here
}
Personally, I wouldn’t call it ugly, either, but that’s mostly a matter of taste
Well, you’d typically put the loops into a function and then do an explicit return to jump out of there. I believe, there’s some use-cases where this isn’t possible, which is why I’m cool with loop labels existing, but I’ve been coding Rust for seven years and have not needed them once…
Sorry, I love Rust but I can’t really agree with you here. They only showed a
macro_rules!definition, which is definitely rust syntax. Lifetime annotations are relatively common.I will concede that loop labels are incredibly rare though.
https://fprijate.github.io/tlborm/mbe-macro-rules.html#%3A~%3Atext=macro_rules!+With%2Cfollowing+form%3A
I guess I see what you mean if we want to get very technical about what a syntax extension is. But I think for the purpose of this discussion, it’s reasonable to think of
macro_rules!as a part of the Rust language. Practically speaking, it is syntax provided by the language team, not just users of the language who are free to extend the syntax by usingmacro_rules!to do so.Loop labels are rare, but they lead to much simpler/clearer code when you need them. Consider how you would implement this kind of loop in a language without loop variables:
'outer: while (...) { 'inner: while (...) { if (...) { // this breaks out of the outer loop, not just the inner loop break 'outer; } } // some code here }In C/C++ you’d need to do something like
bool condition = false; while (...) { while (...) { if (...) { condition = true; break; } } if (condition) { break; } // some code here }Personally, I wouldn’t call it ugly, either, but that’s mostly a matter of taste
Well, you’d typically put the loops into a function and then do an explicit
returnto jump out of there. I believe, there’s some use-cases where this isn’t possible, which is why I’m cool with loop labels existing, but I’ve been coding Rust for seven years and have not needed them once…