Philosophy and "for" loops — more from Go and Rust

Philosophy and "for" loops — more from Go and Rust

This is wrong:

"for statement has some properties of a coroutine, but cannot define local variables for use throughout the loop."

C99 (aka C for anybody not stuck with Visual Studio) allows declaring locally scoped identifiers in "clause-1", where a for loop is defined like "for (clause-1; expression-1; expression-2) { ... }".

for (int x = 0, y = 10; x < y; x++) {
    printf("x:%d\n", x);
}

The only limitation is that you can only declare identifiers of a single type. Theoretically you can get quite sophisticated by doing stuff like:

for (struct { int y; } x = { 0 }; x.y < 10; x.y++) {
    printf("x.y:%d\n", x.y);
}

GCC is cool with that, but clang chokes. I can't find any justification for clang's failure here. In any event, clang will accept a declaration of a compound object in clause-1, you just need to use a named type.

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