[expr.shift] more precise wording for arithmetic shift rounding CWG2724 by eisenwave · Pull Request #6225 · cplusplus/draft (original) (raw)

Problems with the present wording

rounded down

is sometimes used to describe rounding towards zero, and sometimes to describe rounding towards negative infinity. For example, Java uses java.math.RoundingMode.DOWN to describe rounding towards zero.

It is intuitively clear to the committee and to implementers that this should mirror the semantics of the "arithmetic right shift" instruction (which rounds towards negative infinity), but the wording is not so clear.

Improvements made by the suggested wording

rounded towards negative infinity

is unambiguous.
The wording is also quite popular, e.g. the Wikipedia article on rounding uses it.