Re: How do you compare char strings in an elegant way?

"Daniel T." <>
Mon, 8 Oct 2007 01:11:48 CST
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In article <>, wrote:

I have this very simple task, but I cant get it to work:

there is this
std::map<const char* str, int> my_map;
and I would like to compare the requested strings using strcmp.

It works like this :
bool comp(const char* s1, const char* s2)
    return _stricmp(s1, s2) < 0;


A neat solution would be to model the function with STL functor
objects in a combination similiar to
bind2nd(less(strcmp), 0);

which is total garbage, but maybe you get the idea.
thank you

typedef compose_f_gxy_t<binder2nd<less<int> >,
        pointer_to_binary_function<const char*, const char*, int> > ltstr;

map<const char*, int, ltstr > my_map(
        compose_f_gxy( bind2nd( less<int>(), 0 ), ptr_fun( &strcmp ) ) );

To use the above you need a compose functor:

// (C) Copyright Nicolai M. Josuttis 1999.
// Permission to copy, use, modify, sell and distribute this software
// is granted provided this copyright notice appears in all copies.
// This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.

/* class for the compose_f_gxy adapter */
     template <class OP1, class OP2>
class compose_f_gxy_t :
        public std::binary_function<typename OP2::first_argument_type,
        typename OP2::second_argument_type, typename OP1::result_type>
     OP1 op1; // process: op1(op2(x,y))
     OP2 op2;
     // constructor
     compose_f_gxy_t ( const OP1& o1, const OP2& o2 ) :
        op1( o1 ), op2( o2 ) {

     // function call
     typename OP1::result_type operator() (
           const typename OP2::first_argument_type& x,
           const typename OP2::second_argument_type& y ) const {
        return op1( op2( x, y ) );

/* convenience function for the compose_f_gxy adapter */
     template <class OP1, class OP2>
inline compose_f_gxy_t<OP1, OP2> compose_f_gxy (
        const OP1& o1, const OP2& o2 ) {
     return compose_f_gxy_t<OP1, OP2>( o1, o2 );

Now the question is, can this be done with the boost lambda library? It
would probably look much cleaner.

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