On Friday, 16 March 2018 at 17:41:22 UTC, H. S. Teoh wrote:
Given a forward range r, I want to test whether it has exactly
n elements that satisfy some given predicate pred. Is it
possible to do this using current Phobos algorithms such that
it does not traverse more members of the range than necessary?
The naïve solution `r.count!pred == n` walks the entire range,
even though it may already have seen n+1 elements that
satisfies pred, and therefore should already know that the
answer must be false.
T
I've implemented these by hand as special cases of count named
countsExactly, countsAtLeast, countsAtMost beginning at
https://github.com/nordlow/phobos-next/blob/3682da65ecb8497946379b41d8027b8292c635a1/src/algorithm_ex.d#L1941
