How to return a reference to structs?

[Ali Çehreli]

On 11/6/21 8:57 AM, Andrey Zherikov wrote:
 > On Saturday, 6 November 2021 at 13:57:47 UTC, Ali Çehreli wrote:
 >> Have you considered std.range.indexed, which should at least cover the
 >> case of accessing:
 >>
 >>   https://dlang.org/phobos/std_range.html#indexed
 >
 > I don't need to iterate over whole collection, but subset of it.

'indexed' does not iterate the collection; just the ones that are in the 
index array. For example, if you have 2 size_t elements in the index 
array, 'indexed' will touch just two elements.

 > As of now I need to be able to iterate over the arguments
 > within a group as well as those that satisfy some condition.

It turns out 'indexed' provides access by reference; so you can even 
mutate the elements:

import std.algorithm;
import std.range;
import std.stdio;

void main() {
   int[] numbers = [ 0, 1, 2, 3, 4, 5 ];

   size_t[] specials = [ 1, 5 ];
   size_t[] moreSpecials = [ 2, 3, 4 ];

   numbers.indexed(specials).each!((ref n) => n *= 10);
   writeln(numbers);
}

The output shows elements 1 and 5 are multiplied by 10:

[0, 10, 2, 3, 4, 50]

I am happy with that solution. ;)

Of course you can use foreach instead of 'each' and apply some filtering 
condition, etc.

Ali