A delegate problem, create delegation in loop

[Denis Shelomovskij]

05.07.2012 9:54, lijie пишет:
> Hi,
>
> My test code:
>
>     import std.stdio;
>     void main() {
>          void delegate()[] functions;
>          foreach (i; 0 .. 5) {
>              functions ~= {
>                  printf("%d\n", i);
>              };
>
>          }
>          foreach (func; functions) {
>              func();
>          }
>     }
>
>
> output:
>     5
>     5
>     5
>     5
>     5

This program behaves as expected. Just like C# program that will give 
the same output:
---
delegate void MyFunc();

class Program
{
     static void Main()
     {
         var funcs = new MyFunc[5];

         for (int i = 0; i < funcs.Length; ++i)
             funcs[i] = new MyFunc(() => System.Console.WriteLine(i));

         foreach (var f in funcs)
             f();
     }
}
---

because "i" is the same for every iteration. Different situation is for 
such C# loop:
---
for (int i = 0; i < funcs.Length; ++i)
{
     int t = i;
     funcs[i] = new MyFunc(() => System.Console.WriteLine(t));
}
---
where "t" is local for scope. Here C# behaves correctly, but D doesn't. 
This D loop
---
foreach(i; 0 .. 5) {
     int t = i;
     functions ~= { printf("%d\n", t); };
}
---
prints "4" five times. It's Issue 2043:
http://d.puremagic.com/issues/show_bug.cgi?id=2043

I'm not posting workaround here because bearophile already did it.

-- 
Денис В. Шеломовский
Denis V. Shelomovskij