[Issue 8571] New: Defined exception for unequal zip lengths with StoppingPolicy.requireSameLength

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=8571

           Summary: Defined exception for unequal zip lengths with
                    StoppingPolicy.requireSameLength
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody at puremagic.com
        ReportedBy: bearophile_hugs at eml.cc


--- Comment #0 from bearophile_hugs at eml.cc 2012-08-21 04:41:41 PDT ---
This is part of Zip.empty() of Phobos:


@property bool empty()
{
    final switch (stoppingPolicy)
    {
...
    case StoppingPolicy.requireSameLength:
        foreach (i, Unused; R[1 .. $])
        {
            enforce(ranges[0].empty ==
                    ranges.field[i + 1].empty,
                    "Inequal-length ranges passed to Zip");
        }
        return ranges[0].empty;
    }


I suggest to replace that enforce() with a throw of a definite exception, named
like ZipUnequals or something like that, that allows for a clean catch:
catching the enforce() exception is easy, but you can't be sure you are
catching that specific zip enforce instead of another one or a bug.

Knowing that a zip(StoppingPolicy.requireSameLength, ...) has thrown an
exception for unequal lengths is sometimes useful. When you want to use the zip
results and you want to make sure they are equal in length, you want to catch
just that specific length problem.

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