regarding the usage of set_difference with maps

[sdilip519]

i am using maps with a string in the template argument and i want to
find the difference of two maps into another amp for this i can use the
set_difference function but the arguments of the functions are
iterators.
can any one help me in this how to send the arguments in
to the function.

Thanks in advance.

Regards
Dilip

 

[Ian Collins]

i am using maps with a string in the template argument and i want to
find the difference of two maps into another amp for this i can use the
set_difference function but the arguments of the functions are
iterators.
can any one help me in this how to send the arguments in
to the function.

set_difference( first.begin(), first.end(),
second.begin(), second.end(),
result.begin() );

 

[sdilip519]

this is the same i have done but i am getting an stdair error asking
some operator should be over loaded . for this i am attaching the code
which i have used.....


#include <map>
#include <algorithm>
#include <functional> // For greater<int>( )
#include <iostream>
#include<vector>

using namespace std;

int main( )
{

map<char*,int> mapobj1;
map<char*,int> mapobj2;
map<char*,int> mapobj3;

mapobj1["one"] = 111;
mapobj1["two"] = 112;
mapobj1["three"] = 113;
mapobj1["four"] = 114;

mapobj2["five"] = 111;
mapobj2["two"] = 112;
mapobj2["three"] = 113;
mapobj2["four"] = 124;

set_difference(mapobj1.begin(),mapobj1.end(),mapobj2.begin(),mapobj2.end(),mapobj3.begin());


}


and the error is


error C2582: 'std:air<char * const,int>' : 'operator =' function is
unavailable

 

[Pete Becker]

set_difference( first.begin(), first.end(),
second.begin(), second.end(),
result.begin() );

set_difference(first.begin(), first.end(),
second.begin(), second.end(),
back_inserter(result), pred);

where pred takes two pair objects and compares them appropriately. Since
result is a map, you can't overwrite its values, so you need back_inserter.