std.algorithm for changing array values

[bearophile]

Kapps:

> One thing to keep in mind is that structs are passed by value, 
> so this foreach would be operating on a copy of the entry. So
> your setting the value to 42 would have no effect.
>
> Instead you would need "foreach(ref entry; entries)" in order to
> have the change take effect (regardless of whether or not you 
> use std.algorithm).

This is a common bug in D code, especially in code of D newbies, 
but it's also occasionally present in the code of more seasoned D 
programmers.

One solution to avoid it that I suggested is that on default 
foreach yields const values. So if you want to mutate the value 
you have to add a "mutable" or "ref":

foreach (mutable entry; entries) {

Another language solution is to iterate by reference on default, 
so the ref is implicit:

foreach (entry; entries) {

And if you want to iterate by value you need to write something 
different.

There are other solutions. But none of them were accepted by 
Walter :-(

Bye,
bearophile