August 18, 2013
http://d.puremagic.com/issues/show_bug.cgi?id=10845

           Summary: std.range.Cycle broken for reference type forward
                    ranges
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody@puremagic.com
        ReportedBy: peter.alexander.au@gmail.com


--- Comment #0 from Peter Alexander <peter.alexander.au@gmail.com> 2013-08-18 04:59:56 PDT ---
import std.stdio;
import std.range;
import std.algorithm;

void main()
{
    auto a = inputRangeObject(iota(3).filter!"true");
    writeln(a.cycle.take(10));
}

Outputs

[0, 1, 2, 0, 1, 2,

then asserts: http://dpaste.dzfl.pl/84de028d

The problem is Cycle.popFront:

void popFront()
{
    _current.popFront();
    if (_current.empty) _current = _original;
}

It should be _current = _original.save, otherwise the _original range is consumed on the second iteration.

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August 18, 2013
http://d.puremagic.com/issues/show_bug.cgi?id=10845


monarchdodra@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |monarchdodra@gmail.com


--- Comment #1 from monarchdodra@gmail.com 2013-08-18 05:47:49 PDT ---
(In reply to comment #0)
> import std.stdio;
> import std.range;
> import std.algorithm;
> 
> void main()
> {
>     auto a = inputRangeObject(iota(3).filter!"true");
>     writeln(a.cycle.take(10));
> }
> 
> Outputs
> 
> [0, 1, 2, 0, 1, 2,
> 
> then asserts: http://dpaste.dzfl.pl/84de028d
> 
> The problem is Cycle.popFront:
> 
> void popFront()
> {
>     _current.popFront();
>     if (_current.empty) _current = _original;
> }
> 
> It should be _current = _original.save, otherwise the _original range is consumed on the second iteration.

I have an open pull for improving cycle: https://github.com/D-Programming-Language/phobos/pull/1149

So I integrated the fix in it. That said, given how often my pulls get reviewed and pulled, it might be best if you created a pull for this that _I_ could review and pull...

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