通过引用或值传递函数？

Question

#include <iostream>
#include <algorithm>
using namespace std;

bool myfn(int i, int j) { return i<j; }



int main () {
int myints[] = {3,7,2,5,6,4,9};

 // using function myfn as comp:
cout << "The smallest element is " << *min_element(myints,myints+7,myfn) << endl;
cout << "The largest element is " << *max_element(myints,myints+7,myfn) << endl;

return 0;
}

considering the above code , is there any difference if we pass myfn or &myfn to min_element ? when we tried to pass a functor which one would be a more standard way?

Answer 1

Typically, pass-by-reference and pass-by-value only refer to passing variables, not functions. (Template functions introduce some complications, but that is for another discussion.) Here you are passing myfn as a pointer to a function. There is no difference if you use &myfn instead. The compiler will implicitly convert myfn to a pointer to the function with that name.

Answer 2

is there any difference if we pass myfn or &myfn to min_element?

No. myfn gets implicitly converted into pointer-to-function , anyway. So there is no difference at all.