On Tuesday, 22 April 2014 at 11:41:41 UTC, Jay Norwood wrote:
Wow, joiner is much slower than join. Such a small choice can
make this big of a difference. Not at all expected, since the
lazy calls, I thought, were considered to be more efficient.
This is with ldc2 -O2.
Yeah, that's because join actually works on "RoR, R", rather than
"R, E". This means if you feed it a "string[], string", then it
will actually iterate over individual *characters*. Not only
that, but since you are using char[], it will decode them too.
"join" is faster for 2 reasons:
1) It detects you want to joins arrays, so it doesn't have to
iterate over them: It just glues them "slice at once"
2) No UTF decoding.
I kind of wish we had a faster joiner, but I think it would have
made the call ambiguous.
