Understanding switch + foreach

[Ali Çehreli]

Firest, complete code to save others' time:

import std.stdio;
import std.typetuple;

void main()
{
     immutable key = 3;
     switch (key)
     {
         foreach (c; TypeTuple!(1, 2, 3, 4, 5))
         {
             case c: "Found %s!".writefln(c);
                     break;
         }
         break; // Default always gets executed without this break.
         default:
             "Not found %s :(".writefln(key);
             break;
     }
}

On 04/07/2014 03:30 PM, Matej Nanut wrote:

 > I don't understand why so many break statements are needed in this 
construct:
 >
 >      immutable key = 3;
 >      switch (key)
 >      {
 >          foreach (c; TypeTuple!(1, 2, 3, 4, 5))

Ok, that's a compile-time foreach.

 >          {
 >              case c: "Found %s!".writefln(c);
 >                      break;

That's interesting. Since a compile-time foreach is expanded at compile 
time, what happens to a break statement in it? Do we break out of the 
foreach statement or do we insert a break statement?

Apparently, the break inside foreach belongs to the switch-case.

 >          }
 >          break; // Default always gets executed without this break.
 >          default:

I think needing that break is a bug. Meanwhile, moving the default block 
before the foreach seems to be a workaround.

 >              "Not found %s :(".writefln(key);
 >              break;
 >      }
 >
 > One after each case and another one after the foreach.
 >
 > Thanks,
 > Matej
 >

Ali