When using the STL, I'd often want to instantiate an anonymous functor -- something like this:
#include <set>
#include <algorithm>
int main()
{
std::set<int> s;
s.insert(1); s.insert(2);
class
{
public:
bool operator () (int a, int b) { return a < b; }
} comparer;
bool test = comparer(1, 2); // Works
return *( std::max_element(s.begin(), s.end(), comparer) ); // Fails!
} The problem is, under gcc, this fails with the error
test.cpp:17: error: no matching function for call to ‘max_element(std::_Rb_tree_const_iterator<int>, std::_Rb_tree_const_iterator<int>, main()::<anonymous class>&)’
Looking at the <algorithm> header, I say that the error message makes no sense, and the program should compile just fine.
Now it seems that the only way for me to use a functor is to make its class global. But isn't there a way to somehow avoid cluttering the global namespace and keep the code beautiful? Or should I report a bug in the gcc? :-)
May 30th, 2006, 8:09 PM
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