Arrays passed by almost reference?

[Leandro Lucarella]

Andrei Alexandrescu, el  5 de noviembre a las 16:10 me escribiste:
> Ali Cehreli wrote:
> >Thanks for all the responses.
> >
> >And yes, I know that 'ref' is what works for me here. I am trying to figure out whether I should develop a guideline like "always pass arrays with 'ref', or you may face surprises."
> >
> >I understand it very well now and was able to figure out a way to cause some bugs. :)
> >
> >What can be said about the output of the following program? Will main.a[0] be printed as 1 or 111?
> >
> >import std.cstream;
> >
> >void modify(int[] a)
> >{
> >    a[0] = 1;
> >
> >    // ... more operations ...
> >
> >    a[0] = 111;
> >}
> >
> >void main()
> >{
> >    int[] a;
> >    a ~= 0;
> >    modify(a);
> >
> >    dout.writefln(a[0]);
> >}
> >
> >It depends on the operations in between the two assignments to a[0] in 'modify':
> >
> >- if we leave the comment in place, main.a[0] is 111
> >
> >- if we replace the comment with this code
> >
> >    foreach (i; 0 .. 10) {
> >        a ~= 2;
> >    }
> >
> >then main.a[0] is 1. In a sense, modify.a caused only "some" side effects in main.a. If we shorten the foreach, then main.a[0] is again 111. To me, this is at an unmanagable level. Unless we always pass with 'ref'.
> >
> >I don't think that this is easy to explain to a learner; and I think that is a good indicator that there is a problem with these semantics.
> 
> The ball is in your court to define better semantics.

Just make arrays a reference value, like classes!

-- 
Leandro Lucarella (AKA luca)                     http://llucax.com.ar/
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