Remainder is not modulus, but int::rem() uses the mod operator.

[wting]

It turns out that Rust's % behavior mimics C99 (adopting the sign of the dividend). However the modulus and remainder are not the same, but Rust's implementation of int::rem() simply uses the % operator:

#[inline(always)]
pub pure fn rem(x: T, y: T) -> T { x % y }

Shouldn't int::rem()'s behavior be different? Why would Rust have two names for the same action?

ping @graydon

[Kimundi]

I think to be consistent with C, rust should keep the % behavior as it is, but explicitly define it as the 'remainder' operation (with documentation pointing out that it's the same as Cs mod, but mathematically correct named).
That means renaming Num::module() to Num::rem(), and defining the actual mod method in a way that doesn't easily get confused with rem.

[graydon]

These bugs make me a bit dizzy. Did #5990 fix this?

[thestinger]

Yeah, this is fixed now. The rem function should be removed and a modulo function as a wrapper around % can be provided.