std random

[Ed Smith-Rowland]

Greetings,

A while back I noted that the std random was different from the tr1 
random facility.  My original plan was to simply rename the classes in 
the std implementation.  Further investigation into the latest CD for 
C++-0X revealed that the differences were far more pervasive and deeper 
that simply renaming (even renaming involved more hacking of TR1 than 
would make it worth while).

The attached patch splits the random facility.  It also goes a long way 
toward completing the std random facility.  The new analytic type 
distributions were obtained by studying the gmp implementations.  The 
sampling distributions are completely new as are two new engine 
adaptors: independent_bits and shuffle_order.  The generate_canonical 
and the seed_seq utilities are also new.  Even the engines and the 
distributions that have direct analogs in tr1 have been substantially 
reworked due to the changes in design in the later drafts.

This patch is a tad more aggressive than one would want at this stage 
;-).  This would only go in for 4.5 I think.  That leaves the question 
of what we should do for 4.4.  I think it may be misleading to keep 
random in std.  I think it may be best to simply delete or disable 
include/std/random for now.  What do all of you you think?

The patch bootstraps and regtests with no new fails on 
x86_64-unknown-linux-gnu.

The one thing that I must figure out before release is that one of the 
constructor overloads:
template<typename SeedSeq>
  some_engine(SeedSeq& sseq);

eats a lot of calls that it shouldn't such as this:

some_engine(unsigned long seed);

and barfs because unsigned long doesn't have a generate() method.

I need to kind of pseudo-concept for SeedSeq.  Any pointers on how this 
mechanism works in gcc would be helpful.  I'm just starting to look at 
this.  I need to request that a type support a generate(Iter,Iter) 
method before being worthy of the first ctor.

I'll make a list of other issues more specific to random that I and 
others could help think about in another message.

Thank you,

Ed

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