[STDCXX-126] std::random_shuffle ambiguity with RandomNumberGenerator

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 4.1.3
• Fix Version/s: 4.1.4
• Component/s: 25. Algorithms

Environment

all

• Assignee: Martin Sebor
• Reporter: Martin Sebor
• Created: 26/Jan/06 09:33
• Updated: 22/Apr/08 02:59
• Resolved: 28/Feb/06 10:35

Description

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 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