http://d.puremagic.com/issues/show_bug.cgi?id=4664

           Summary: Lambdas default arguments problems
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2010-08-17 07:15:28 PDT ---
In C++0x default arguments are not allowed in lambdas. In D2 they are allowed, but this program shows (compiled with dmd 2.048) that they have problems:


import std.stdio: writeln;
void foo(T)(T callme) {
    callme();
}
void main() {
    auto lam1 = (int x=5){ writeln(x); };
    auto lam2 = (int x=10){ writeln(x); };
    foo(lam1);
    foo(lam2);
}



Output:
5
5


Is it positive to disallow default arguments in D2 lambdas too?

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Jonathan M Davis <jmdavisProg@gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |jmdavisProg@gmail.com


--- Comment #1 from Jonathan M Davis <jmdavisProg@gmail.com> 2010-08-17 16:42:10 PDT ---
I would think that it would be better if the two didn't conflict as opposed to getting rid of default parameters. It looks like they're being turned into the same function when they're not (at least conceptually) - one because they have different default parameters, and two because they're lambdas, not functions with names.

Now, assuming that it can't be fixed so that these functions are actually separate like you'd think that they'd be, then it would probably be better to disallow default arguments, but I'd argument that this is a compiler bug rather than a bug in the language.

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nfxjfg@gmail.com changed:

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                 CC|                            |nfxjfg@gmail.com


--- Comment #2 from nfxjfg@gmail.com 2010-08-17 16:59:15 PDT ---
Is this a dupe of bug #4028?
Short story: dmd merges the two delegate types into one, and the first default
value "wins".

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--- Comment #3 from Jonathan M Davis <jmdavisProg@gmail.com> 2010-08-17 19:12:50 PDT ---
It does look like it's essentially a duplicate, though the way that the problem is hit is a bit different.

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Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

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                 CC|                            |andrej.mitrovich@gmail.com


--- Comment #4 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2010-08-30 06:35:48 PDT ---
As a quick hack while this isn't fixed you can use this:

    auto lam1 = function (int x=5){ writeln(x); };
    auto lam2 = delegate (int x=10){ writeln(x); };

But this will only work with 2 lambdas at most, and it isn't very nice. :)

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yebblies <yebblies@gmail.com> changed:

           What    |Removed                     |Added
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             Status|NEW                         |RESOLVED
                 CC|                            |yebblies@gmail.com
         Resolution|                            |DUPLICATE


--- Comment #5 from yebblies <yebblies@gmail.com> 2011-06-08 07:30:12 PDT ---
*** This issue has been marked as a duplicate of issue 4028 ***

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