[Boost-users] Bind question

From: Surya Kiran Gullapalli (skg_at_[hidden])
Date: 2005-02-07 07:49:33

Hi all,
This is a follow up to my previous message on boost::bind question.

Please go thru the attached program.

I've 2 structures X an Y, and i'm calling stable_sort on vectors of both
the objects. 
But in one stable sort, i'm using the member variable directly, and in
the other i'm using a member function to access that.

When i use boost::bind with member variable directly, it has no problem
(structure Y),
But if i use member function to access the member variable, which is
private, i'm getting compilation errors,  The essence of the compilation
error is given below..

=====================
./boost/include/boost/lambda/detail/actions.hpp:86: error: no matching
function for call to `boost::lambda::function_adaptor<int
(X::*)()>::apply(int (X::*const&)(), const X&)'
./boost/include/boost/lambda/detail/function_adaptors.hpp:193: note:
candidates are: static Result boost::lambda::function_adaptor<Result
(Object::*)()>::apply(Result (Object::*)(), Object*) [with RET = int,
Object = X, Result = int]
./boost/include/boost/lambda/detail/function_adaptors.hpp:197: note:
static Result boost::lambda::function_adaptor<Result
(Object::*)()>::apply(Result (Object::*)(), Object&) [with RET = int,
Object = X, Result = int]
=====================

what am i doing wrong.
thanks in advance,
Surya


#include <boost/lambda/lambda.hpp>
#include <boost/lambda/bind.hpp>

#include <iostream>
#include <vector>
#include <algorithm>

using namespace boost::lambda ;
using namespace std ;

struct X
{
        private:
                int a ;
        public:
                X () {}
                int get_a() { return a ; }
                void set_a (int var) { a = var ;}
} ;

struct Y
{
        int a ;
} ;

int main (void)
{
        vector <X> vx ;
        vector <Y> vy ;
        X varx1; varx1.set_a(5) ; vx.push_back (varx1) ;
        X varx2; varx2.set_a(8) ; vx.push_back (varx2) ;
        X varx3; varx3.set_a(7) ; vx.push_back (varx3) ;
        X varx4; varx4.set_a(4) ; vx.push_back (varx4) ;
        X varx5; varx5.set_a(9) ; vx.push_back (varx5) ;
        X varx6; varx6.set_a(2) ; vx.push_back (varx6) ;
        X varx7; varx7.set_a(6) ; vx.push_back (varx7) ;

        Y vary1; vary1.a = 5  ; vy.push_back (vary1) ;
        Y vary2; vary2.a = 8  ; vy.push_back (vary2) ;
        Y vary3; vary3.a = 7  ; vy.push_back (vary3) ;
        Y vary4; vary4.a = 4  ; vy.push_back (vary4) ;
        Y vary5; vary5.a = 9  ; vy.push_back (vary5) ;
        Y vary6; vary6.a = 2  ; vy.push_back (vary6) ;
        Y vary7; vary7.a = 6  ; vy.push_back (vary7) ;

        cout << "BEFORE SORT" << '\t' ;
        for_each (vy.begin(), vy.end(), cout << bind (&Y::a, _1) << '\t') ;
        cout << endl ;
        stable_sort (vy.begin(), vy.end(), bind (less<int>(), bind (&Y::a, _1), bind (&Y::a, _2))) ;
        cout << "AFTER SORT" << '\t' ;
        for_each (vy.begin(), vy.end(), cout << bind (&Y::a, _1) << '\t') ;
        cout << endl ;
#if 0
        cout << "BEFORE SORT" << '\t' ;
        for_each (vx.begin(), vx.end(), cout << bind (&X::get_a, _1) << '\t') ;
        cout << endl ;
        stable_sort (vx.begin(), vx.end(), bind (less<int>(), bind (&X::get_a, _1), bind (&X::get_a, _2))) ;
        cout << "AFTER SORT" << '\t' ;
        for_each (vx.begin(), vx.end(), cout << bind (&X::get_a, _1) << '\t') ;
        cout << endl ;
#endif
        return 0 ;
}