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c++atoi

How do I fix a "no matching function for call to 'atoi'" error?

All indications tell me this is a ridiculously easy problem to solve, but I can't figure out error telling me the atoi function doesn't exist.

C++

#include <iostream>
#include <stdlib.h>

using namespace std;

string line;
int i;

int main() {

    line = "Hello";
    i = atoi(line);
    cout << i;

    return 0;
}


Error

lab.cpp:18:6: error: no matching function for call to 'atoi'
i = atoi(line);
    ^~~~
Solution

  • atoi expects const char*, not an std::string. So pass it one:

    i = atoi(line.c_str());

    Alternatively, use std::stoi:

    i = std::stoi(line);