RefRange

[David]

Am 26.08.2012 18:06, schrieb Ali Çehreli:
> On 08/26/2012 08:41 AM, David wrote:
>> It's a RefRange, but not completly ... Can somebody explain me that
>> behaviour?
>>
>> http://dpaste.dzfl.pl/643de2a3
>
> According to its documentation, RefRange works differently whether the
> original range is a ForwardRange or not:
>
>    http://dlang.org/phobos/std_range.html#refRange
>
> I have made TestRange a ForwardRange but then I had to comment out two
> lines of your program. Does it work according to your expectations with
> this change?
>
> import std.stdio;
> import std.range;
>
> struct TestRange {
>      float[] x = [0, 1, 2, 3, 4, 5];
>
>      @property bool empty() {
>          return x.length == 0;
>      }
>
>      @property ref float front() {
>          return x[0];
>      }
>
>      void popFront() {
>          //writefln("before: %s", x);
>          x = x[1..$];
>          //x.popFront();
>          //writefln("after: %s", x);
>      }
>
>      TestRange save() @property {
>          return TestRange(x);
>      }
> }
>
>
>
> void main() {
>      static assert(isForwardRange!TestRange);
>
>      TestRange r = TestRange();
>      auto rr = refRange(&r);
>
>      //    foreach(element; rr) {}
>
>      //    writefln("Original range: %s", r.x);
>      //    writefln("RefRange: %s", rr.x);
>
>      writefln("%s - %s", r.x.ptr, r.x.ptr);
>
>      rr.popFront();
>
>      writefln("%s - %s", r.x.ptr, r.x.ptr);
>      writefln("Original range: %s", r.x);
>      // We can't expect the RefRange to have the members of the original
> range
>      // writefln("RefRange: %s", rr.x);
>
>      r.popFront();
>
>      writefln("%s - %s", r.x.ptr, r.x.ptr);
>      writefln("Original range: %s", r.x);
>      // We can't expect the RefRange to have the members of the original
> range
>      // writefln("RefRange: %s", rr.x);
> }
>
> Ali

Yes, that does it, but .save doesn't play well with RefRange (a static 
assert inside RefRange fails, telling that the produced RefRange-Type is 
not a ForwardRange).