foreach over pointer to range

[Artur Skawina]

On 06/05/12 22:23, simendsjo wrote:
> On Tue, 05 Jun 2012 20:46:51 +0200, Timon Gehr <timon.gehr at gmx.ch> wrote:
> 
>>
>> It should be dropped. A pointer to range is a perfectly fine range.
> 
> 
> Sure..? I couldn't get it to work either:
> struct R {
>     string test = "aoeu";
>     @property front() { return test[0]; }
>     @property bool empty() { return !test.length; }
>     void popFront(){test = test[0..$];}
> }
> 
> void main() {
>     R r;
>     R* p = &r;
>     foreach(ch; p) // invalid foreach aggregate p
>         writeln(ch);
> }

It /is/ a valid range, but it's /not/ currently accepted
by foreach.

So you have to write the above as:
   
   struct R {
       string test = "aoeu";
       @property front() { return test[0]; }
       @property bool empty() { return !test.length; }
       void popFront(){test = test[0..$];}
   }

   struct RangePtr(R) {
      R* ptr;
      alias ptr this;
      @property front()() { return ptr.front; }
   }

   void main() {
       R r;
       auto p = RangePtr!R(&r);
       foreach(ch; p)
           writeln(ch);
   }

which works, but only obfuscates the code and can be less efficient.

artur