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From "Martin Sebor (JIRA)" <j...@apache.org>
Subject [jira] Resolved: (STDCXX-126) std::random_shuffle ambiguity with RandomNumberGenerator
Date Tue, 28 Feb 2006 01:36:55 GMT
     [ http://issues.apache.org/jira/browse/STDCXX-126?page=all ]
     
Martin Sebor resolved STDCXX-126:
---------------------------------

    Resolution: Fixed

Fixed with the referenced change. The test case compiles successfully.

> std::random_shuffle ambiguity with RandomNumberGenerator
> --------------------------------------------------------
>
>          Key: STDCXX-126
>          URL: http://issues.apache.org/jira/browse/STDCXX-126
>      Project: C++ Standard Library
>         Type: Bug
>   Components: 25. Algorithms
>     Versions: 4.1.3
>  Environment: all
>     Reporter: Martin Sebor
>     Assignee: Martin Sebor
>     Priority: Minor
>      Fix For: 4.1.4

>
> From 25.2.11, p3 [lib.alg.random.shuffle]:
> -3- Note random_shuffle() can take a particular random number generating function object
rand such that if n is an argument for rand, with a positive value, that has type iterator_traits<RandomAccessIterator>::difference_type,
then rand(n) returns a randomly chosen value, which lies in the interval [0, n), and which
has a type that is convertible to iterator_traits<RandomAccessIterator>::difference_type.
> The program below conforms to the requirement above yet  fails to compile:
> $ cat t.cpp && make t
> #include <algorithm>
> #include <iterator>
> #include <cstddef>
> template <class IntT>
> struct Generator
> {
>     struct DiffConvertible {
>         DiffConvertible (IntT) { }
>         operator IntT () const { return IntT (); }
>     };
>     DiffConvertible operator() (DiffConvertible n) const {
>         return DiffConvertible (IntT (n));
>     }
> private:
>     void operator() (unsigned) { }
>     void operator() (unsigned long) { }
> };
> int main ()
> {
>     Generator<std::iterator_traits<int*>::difference_type> gen;
>     std::random_shuffle<int*>(0, 0, gen);
> }
> gcc -c -I/build/sebor/dev/stdlib/include/ansi -D_RWSTDDEBUG   -pthreads -D_RWSTD_USE_CONFIG
-I/build/sebor/gcc-4.0.2-15s/include -I/build/sebor/dev/stdlib/include -I/build/sebor/dev/stdlib/../rwtest
-I/build/sebor/dev/stdlib/../rwtest/include -I/build/sebor/dev/stdlib/tests/include  -pedantic
-nostdinc++ -g  -W -Wall -Wextra -Wcast-qual -Winline -Wshadow -Wwrite-strings -Wno-long-long
 t.cpp
> /build/sebor/dev/stdlib/include/algorithm.cc: In function 'void std::random_shuffle(_RandomAccessIter,
_RandomAccessIter, _RandomNumberGenerator&) [with _RandomAccessIter = int*, _RandomNumberGenerator
= Generator<int>]':
> t.cpp:26:   instantiated from here
> t.cpp:18: error: 'void Generator<IntT>::operator()(unsigned int) [with IntT = int]'
is private
> /build/sebor/dev/stdlib/include/algorithm.cc:594: error: within this context
> t.cpp:26:   instantiated from here
> /build/sebor/dev/stdlib/include/algorithm.cc:594: error: void value not ignored as it
ought to be
> make: *** [t.o] Error 1

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