Error: Expression must have (Pointer-to-) function type

Question

I am writing a function that spits out what are called Stirling numbers. The code that I've written is as follows:

int SecondStirling(const int& k, const int&n){
    if(k<0||n<0) return 0;
    if(k==0 && n>0) return 0;
    if(k>0 && n==0) return 0;
    if(k>n) return 0;
    if(k==n) return 1;
    else return k(SecondStirling(k,n-1))+SecondStirling(k-1,n-1);
}

However, I am getting an error on the last line: Error: Expression must have (Pointer-to-) function type, the error specifically referring to k. What gives?

Solution 1

Unlike in math, the multiplication operator * can't be omitted. Change

k(SecondStirling(k,n-1))

to

k * (SecondStirling(k,n-1))

Solution 2

By writing

k(SecondStirling(k,n-1))

You are trying to call a function named "k", or pointed by "k", accepting a single parameter of type int (which is returned by SecondStirling). However "k" is an int variable, hence the error. The correct syntax, as already pointed out, is

k * (SecondStirling(k,n-1))