On Friday, 16 March 2018 at 17:50:37 UTC, Andrei Alexandrescu
wrote:
On 3/16/18 1:41 PM, 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.
r.count!pred.walkLength(n) == n
Shouldn't this be using filter (count is eager)?
r.filter!pred.walkLength(n) == n
