http://d.puremagic.com/issues/show_bug.cgi?id=5441

           Summary: std.random.rndGen always returns Random.
           Product: D
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: andrei@metalanguage.com
        ReportedBy: repeatedly@gmail.com


--- Comment #0 from Masahiro Nakagawa <repeatedly@gmail.com> 2011-01-10 09:43:40 PST ---
Created an attachment (id=867)
Patch for this suggestion

rndGen always returns Random(usually MT) object. This is often useful, but randomShuffle cant't take other random generators.

I think following signature is better.

    ref RandomGen rndGen(RandomGen = Random)()

But this change forces us to write parenthesis function call.

    rndGen;    // Compilation error
    rndGen();  // OK, return Random object.

For me, this is no problem. However I don't know the writing style of other people.

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Stewart Gordon <smjg@iname.com> changed:

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--- Comment #1 from Stewart Gordon <smjg@iname.com> 2012-04-08 15:33:08 PDT ---
(In reply to comment #0)
> Created an attachment (id=867) [details]
> Patch for this suggestion
> 
> rndGen always returns Random(usually MT) object. This is often useful, but randomShuffle cant't take other random generators.

It can, as of DMD 2.058 at least.  Its signature is

void randomShuffle(Range, RandomGen = Random)(Range r,
        ref RandomGen gen = rndGen)

The two parameters are the range to shuffle and the RNG to use to perform the shuffle.

> I think following signature is better.
> 
>     ref RandomGen rndGen(RandomGen = Random)()

What, exactly, would your rndGen function _do_ to the RandomGen object you pass into it???

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bearophile_hugs@eml.cc changed:

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                 CC|                            |bearophile_hugs@eml.cc


--- Comment #2 from bearophile_hugs@eml.cc 2012-04-08 16:43:35 PDT ---
See also Issue 4851

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Joseph Rushton Wakeling <joseph.wakeling@webdrake.net> changed:

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                 CC|                            |joseph.wakeling@webdrake.ne
                   |                            |t


--- Comment #3 from Joseph Rushton Wakeling <joseph.wakeling@webdrake.net> 2013-05-03 07:38:00 PDT ---
rndGen _should_ always return Random, because rndGen is intended to provide a thread-safe instance of the default RNG type (which _is_ Random).

The problems identified here aren't with rndGen but with code that does not take into account RNG instances other than rndGen.  So, I suggest this bug be marked as invalid.

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