modify the value in pair<>

timothyguo (21)
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vector< pair<string, double> > var_map;

...here pushes pairs into var_map...

var_map.back().second = 4.3;


why can the last line not modify the value stored in the last element of var_map?
What is the right way to do that?
kbw (9488)
why can the last line not modify the value stored in the last element of var_map?
It ought to.

What is the right way to do that?
Looks ok to me, as long as the vector isn't empty.
jsmith (5804)
This works for me:

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#include <string>
#include <utility>
#include <vector>
#include <iostream>

int main() {
    std::vector< std::pair< std::string, double > > var_map;
    var_map.push_back( std::make_pair( std::string( "Hello" ), 3.14 ) );
    var_map.back().second = 1.414;
    std::cout << var_map.back().first << " -> " << var_map.back().second << std::endl;
}

timothyguo (21)
Oh! I made a mistake somewhere else. :-(
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