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digitalmars.D.bugs - [Issue 9493] New: std.algorithm.canFind returns true for empty string in array of integers

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9493

           Summary: std.algorithm.canFind returns true for empty string in
                    array of integers
           Product: D
           Version: D2
          Platform: x86_64
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: monkeyworks12 hotmail.com



It seems that std.algorithm.canFind returns true when checking for the empty
string within an array of integers. This seems like unintended behaviour to me,
so I'm reporting it as a bug. This bug is present on at least DMD 2.061.

Example:
import std.algorithm;

void main()
{
    //This assertion should fail, but doesn't
    assert(canFind([1, 2, 3, 4], ""));
}

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Feb 09 2013
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9493


monarchdodra gmail.com changed:

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





 It seems that std.algorithm.canFind returns true when checking for the empty
 string within an array of integers. This seems like unintended behaviour to me,
 so I'm reporting it as a bug. This bug is present on at least DMD 2.061.
 
 Example:
 import std.algorithm;
 
 void main()
 {
     //This assertion should fail, but doesn't
     assert(canFind([1, 2, 3, 4], ""));
 }


I think this is inteded behavior. You are basically looking for instances of
*nothing*, which, by definition, can be found inside everything (*). I'd expect
a true returned here, and this would be consistent with the rest of the finds
(AFAIK).

Are you getting a different behavior for, say arrays? eg "canFind([1, 2, 3],
(int[]).init)" I don't have access to my compiler, so that's an actual
question. If you *are* getting a different behavior, then I'd argue *that's* a
bug.

*: The only ambiguous case I see is if hasytack is empty, in which case I could
see it both ways, but I'd still lean for "true", since "empty is empty", so
"empty can be found inside empty".

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Feb 10 2013
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9493


Jonathan M Davis <jmdavisProg gmx.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jmdavisProg gmx.com



PST ---
I think that there's a good chance that it's intended behavior that looking for
an empty range with canFind always returns true. However, the fact that canFind
is accepting a _string_ as the needle when the haystack is int[] seems very
wrong.

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Feb 10 2013