Range golf challenge: apply predicate to a subrange, returning the original range modified.

[Ali Çehreli]

On 10/7/22 09:35, Andrey Zherikov wrote:
 > On Friday, 7 October 2022 at 16:32:07 UTC, Andrey Zherikov wrote:
 >> ```d
 >> 10.iota.map!(_ => _.isEven ? _*2 : _); // => [0, 1, 4, 3, 8, 5, 12, 7,
 >> 16, 9]
 >> ```
 >
 > You can even generalize this:
 > ```d
 > alias mapSubrange(alias filter, alias transform) = map!(_ => filter(_) ?
 > transform(_) : _);
 > 10.iota.mapSubrange!(isEven, _ => _*2);
 > ```

I was trying something similar where I left .map to the user code:

import std;

bool isEven(T)(T value) {
     return !(value % 2);
}

alias applyIf(alias pred, alias func) = value => (pred(value) ? 
func(value) : value);

void main() {
     auto result = 10.iota.map!(applyIf!(isEven, a => a * 2));
     assert(result.equal([0, 1, 4, 3, 8, 5, 12, 7, 16, 9]));
}

Ali