[std.algorithm.searching] Add extrema to compute min and max

[ntrel]

Performs < 3n/2 comparisons, unlike the naive < 2n.
Implemented for an input range.
TODO add alias map = a => a parameter, once design is confirmed OK.

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[dkorpel]

@atilaneves This is a new public function

[atilaneves]

unlike the naive < 2n.

Unlike the naive version done where?

[ntrel]

Unlike the naive version done where?

https://dlang.org/phobos/std_algorithm_iteration.html#fold

// Compute minimum and maximum at the same time
writeln(arr.fold!(min, max)); // tuple(1, 5)

[atilaneves]

Unlike the naive version done where?

https://dlang.org/phobos/std_algorithm_iteration.html#fold

// Compute minimum and maximum at the same time
writeln(arr.fold!(min, max)); // tuple(1, 5)

Do you mean min and max? I don't understand what fold has to do with this.

[pbackus]

@atilaneves min and max take pairs of elements, not ranges. The versions that take ranges are called minElement and maxElement.

[RazvanN7]

@ntrel @atilaneves how do we move further with this?

[atilaneves]

I still don't know what this is a replacement for.

[dkorpel]

When a user wants to compute the min and max value of a range with Phobos, currently they need to call minElement and maxElement separately, resulting in 2n comparisons. By using the new extrema function, they're only doing 1.5n comparisons. It's somewhat similar to the sincos function being more efficient than separate sin and cos calls.

[atilaneves]

The explicit ElementType!Range makes me wonder what happens when the elements are const, immutable, or shared.

[PetarKirov]

I think this function should rather return a named tuple:

Tuple!(ElementType!Range, "min", ElementType!Range "max")

[thewilsonator]

PR please!