On Friday, 9 June 2017 at 17:50:28 UTC, Honey wrote:
Looking at the implementation of Tuple.opCmp, I'm not sure I'd
bet on existence of opCmp for fundamental types:
int opCmp(R)(R rhs)
if (areCompatibleTuples!(typeof(this), R, "<"))
{
foreach (i, Unused; Types)
{
if (field[i] != rhs.field[i])
{
return field[i] < rhs.field[i] ? -1 : 1;
}
}
return 0;
}
It turned out that there is a standard three way comparison
function for ranges and strings [1].
Doesn't it make sense to introduce another overload of cmp
similar to Steve's doCmp [2] right at that spot?
This would simplify the implementation of opCmp for aggregates
and can also lead to a moderate performance benefit [3]. (Note
that [3] does not provide an additional overload of cmp but uses
a less elegant approach with the same performance
characteristics.)
// $ ldc2 -O3 -release -boundscheck=off cmpTuple.d
//
// real 0m18.787s
// user 0m18.784s
// sys 0m0.003s
//
//
// $ ldc2 -O3 -release -boundscheck=off cmpTuple.d
-d-version=singlePassCmp
// $ time ./cmpTuple
//
// real 0m16.109s
// user 0m16.102s
// sys 0m0.007s
[1] https://dlang.org/phobos/std_algorithm_comparison.html#cmp
[2] http://forum.dlang.org/post/ohedtb$1phe$1...@digitalmars.com
[3] https://dpaste.dzfl.pl/7cbfa2e1965b
