[Bug libstdc++/43660] range of random-number generator seems wrong/confusing

[Bug libstdc++/43660] range of random-number generator seems wrong/confusing

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43660

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #2)
> (In reply to comment #0)
> > [Note that the same issue exists with other ways of invoking using the
> > generator (e.g., a std::uniform_real_distribution<float> with bounds of
> > 0 and 1 will indeed return 1); but it's less clear its a bug in those
> > cases (although, for instance, boost's random implementation never
> > seems to return the upper bound).]
> 
> Again, referring to the latest draft:
> "A uniform_real_distribution random number distribution produces random
> numbers x, a <= x < b"
> 
> So that does appear to be a bug

PR 64351 deals with that case.

[Bug libstdc++/43660] range of random-number generator seems wrong/confusing

[paolo dot carlini at oracle dot com]

------- Comment #4 from paolo dot carlini at oracle dot com  2010-04-06 11:00 -------
Jon is right and recently I removed that old comment from random.h because
indeed was incorrect.


-- 

paolo dot carlini at oracle dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43660

[Bug libstdc++/43660] range of random-number generator seems wrong/confusing

[redi at gcc dot gnu dot org]

------- Comment #3 from redi at gcc dot gnu dot org  2010-04-06 10:53 -------
(In reply to comment #0)
> 
> As best as I can tell, std::random_shuffle wants its random-number
> generating functor to return results in the range [0,N), where N is the
> parameter it passes to the functor; i.e., the upper-bound is exclusive
> (and the lower-bound inclusive).

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3056.pdf changes the
third random_shuffle overload to shuffle and changes the requirements


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43660

[Bug libstdc++/43660] range of random-number generator seems wrong/confusing

[redi at gcc dot gnu dot org]

------- Comment #2 from redi at gcc dot gnu dot org  2010-04-06 10:40 -------
(In reply to comment #0)
> [Note that the same issue exists with other ways of invoking using the
> generator (e.g., a std::uniform_real_distribution<float> with bounds of
> 0 and 1 will indeed return 1); but it's less clear its a bug in those
> cases (although, for instance, boost's random implementation never
> seems to return the upper bound).]

Again, referring to the latest draft:
"A uniform_real_distribution random number distribution produces random numbers
x, a <= x < b"

So that does appear to be a bug


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43660

[Bug libstdc++/43660] range of random-number generator seems wrong/confusing

[redi at gcc dot gnu dot org]

------- Comment #1 from redi at gcc dot gnu dot org  2010-04-06 10:38 -------
n1933 is ancient history, the RNG pieces have changed significantly

In the current draft it says:
"A uniform_int_distribution random number distribution produces random integers
i, a <= i <= b"

So it is a closed interval [a,b] rather than [a,b)


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43660