[basic.fundamental] p2 `modulo` is ambigous in defining result

[xmh0511]

Full name of submitter (unless configured in github; will be published with the issue): Jim X

[basic.fundamental] p2 says:

arithmetic for the unsigned type is performed modulo 2^N.

Consider this example:

int main(){
   auto r = 2u - 4u;
}

Modulo Wiki says

The rule defines the result as -2 mod 4294967296, which in turn, is determined by what modulo means here. modulo has different definitions on mathematics and computer science, which determines whether the remainder is a positive number or a negative.

Suggested Resolution

arithmetic for the unsigned type is a unique value of that type that is congruent to the result of the arithmetic modulo 2^N

[frederick-vs-ja]

Per search results of "is performed modulo", I find that when one says "is performed modulo" (exactly these 3 English words), the operation is always arithmetic modulo and there doesn't seem any counterexample. Also, I guess the sentence should be moved somewhere in [expr] as it's entirely about evaluation of some expressions.

Concerns here can be handled editorially IMO (if improvements are desired).

arithmetic for the unsigned type is a unique value of that type that is congruent to the result of the arithmetic modulo 2^N

The suggestion seemingly says that "some kind of arithmetic is some value", which seems semantically ill-formed to me. Presumably "produces" should be used instead of "is".

[t3nsor]

agree that this is editorial