Invalid Conversion Error When Using Function Pointers in C++

Question

So I have been trying and battling with this for a few hours now. I am relatively new to c++ but I read about function pointers and it looked pretty useful. Essentially, what I am attempting to do below is to pass two integer values to the function foo and then multiply it by 10. However, I keep getting the following error: "invalid conversion from 'int' to 'int (*)(int, int)' [-fpermissive]".

#include <iostream>

using namespace std;

int foo(int nX, int nY){
    return nX*nY;
}


int multTen(int a, int b, int (*Fn)(int, int)){
    return 10*Fn(a,b);
}

int main(){
    cout << multTen(3,4,foo(3,4)) << endl;
}

Your kind help in this regard is highly appreciated. :)

Mahesh · Accepted Answer · 2012-03-31 15:07:32Z

3

cout << multTen(3,4,foo(3,4)) << endl;
                 // ^^^^^^^ calling function foo and it's return value is passed 
                 // to multTen

The problem is that you are calling the mulTen with the return value of foo as a parameter instead of passing a pointer to it.

answered Mar 31, 2012 at 15:07

Mahesh

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Oliver Charlesworth · Accepted Answer · 2012-03-31 15:07:20Z

2

Did you mean this?

cout << multTen(3,4,foo) << endl;

answered Mar 31, 2012 at 15:07

Oliver Charlesworth

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Comments

psalvaggio · Accepted Answer · 2012-03-31 15:07:23Z

2

Omit the (3,4) on foo. In your code sample, you are calling the foo function with the parameters (3,4) and passing the return value to multTen.

answered Mar 31, 2012 at 15:07

psalvaggio

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