Hi.
On Tue, Jul 15, 2003 at 11:09:26AM -0400, Paul Dubuc wrote:
> Here is a simplified example of some code that compiles and works with g++
> 2.95.3 but gives the following compiler error with g++ 3.3. Can anyone
> tell me
> what is wrong with this code and how to get it to work with the new compiler
> (other than rewriting the loop without find_if and bind2nd)? Help would be
> very
> much appreciated. Thank you.
>
> #include <iostream>
> #include <list>
> #include <functional>
> #include <algorithm>
>
> class FPB {
> private:
> long key;
> public:
> long getkey() const { return key; }
> };
>
> struct compareKey :
> std::binary_function<const FPB, const long*, bool>
> {
> bool operator()(const FPB& pb, const long* key_ptr) const
> {
> return pb.getkey() == *key_ptr;
> }
> };
>
> main()
> {
> std::list<FPB> lst;
> long key = 1;
>
> std::list<FPB>::iterator iter(
> std::find_if(
> lst.begin(),
> lst.end(),
> std::bind2nd(compareKey(), &key)
> )
> );
> if (iter != lst.end()) std::cout << "found" << std::endl;
> else std::cout << "not found" << std::endl;
> }
[snip]
> /vol/gnu/gcc/include/c++/3.3/bits/stl_function.h: In instantiation of
> `std::bind
> er2nd<compareKey>':
> b2nd.cc:34: instantiated from here
> /vol/gnu/gcc/include/c++/3.3/bits/stl_function.h:401: error: `typename
> _Operation::result_type std::binder2nd<_Operation>::operator()(typename
> _Operation::first_argument_type&) const [with _Operation = compareKey]'
> and
> `typename _Operation::result_type
> std::binder2nd<_Operation>::operator()(typename
> _Operation::first_argument_type&) const [with _Operation = compareKey]'
> cannot be overloaded
If you look at the class declaration of binder2nd in
/vol/gnu/gcc/include/c++/3.3/bits/stl_function.h around line 401
you could see the problem.
The problem is that (if _GLIBCPP_RESOLVE_LIB_DEFECTS is defined) the
() operator of binder2nd is overloaded. These are the (simplified)
prototypes:
op::result_type operator() (const op::first_argument_type&) const ;
op::result_type operator() ( op::first_argument_type&) const ;
If you fill in the templatized typenames of your compareKey struct
viz. "const FPB" for "op::first_argument_type" you'd see that the
operator's prototypes are essentially the same which is forbidden, of
course.
If you declare
struct compareKey : std::binary_function<FPB, const long*, bool>
the error is gone. I suppose you'd want to remove the const
modifier on "long*" also, then. Or you could try to undef'ine
_GLIBCPP_RESOLVE_LIB_DEFECTS before bits/stl_function.h gets
included... but that would be kinda wacky, YMMV. :-)
HTH
--
Claudio Bley ASCII ribbon campaign (")
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