How to resolve the error: called object type 'char' is not a function or function pointer-CodePudding

So, in a program I was trying to print a pair from a stack. The code is as follows:

#include <iostream>
#include <stack>
#include <utility>
using namespace std;

int main()
{
    stack<pair<char, int>> deleteOperations;
    stack<pair<pair<char, char>, int>> replaceOperations;
    deleteOperations.push(make_pair('a', 1));
    replaceOperations.push(make_pair(make_pair('b', 'c'), 2));
    cout << deleteOperations.top().first();
    cout << replaceOperations.top().first().first();

    return 0;
}

The error is:

test.cpp:12:41: error: called object type 'char' is not a function or function pointer
    cout << deleteOperations.top().first();
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
test.cpp:13:13: error: type 'std::__1::pair<char, char>' does not provide a call operator
    cout << replaceOperations.top().first().first();
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2 errors generated.

CodePudding user response：

std::pair<>::first is a member variable, not a function, just use deleteOperations.top().first; and replaceOperations.top().first.first