RefRange

[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