c++ - Write a subprogram that calculates n!. While using this subprogram make a program that calculates (a+b)! -

my task

write subprogram calculates n!. while using subprogram make program calculates (a+b)!.

i wrote following code:

using  namespace  std; int f(int n) {     for(int i=1;i<=n;i++){         f=f*i;     }     return f; } int main() {     int a,b;     cout<<"a=";     cin>>a;     cout<<"b=";     cin>>b;     cout<<"factorial of a+b="<<(a+b)*f;     return 0; } 

and error when compile:

 in function 'int f(int)': 7:27: error: invalid operands of types 'int(int)' , 'int' binary 'operator*' 8:8: error: invalid conversion 'int (*)(int)' 'int' [-fpermissive]  in function 'int main()': 16:34: error: invalid operands of types 'int' , 'int(int)' binary 'operator*' 17:9: error: expected '}' @ end of input 

here's error

return f; 

returns function pointer of function f(). you're using function pointer calculations.

in c++ need declare variable can used calculate , return:

int f(int n) {     int result = 1;     for(int i=1;i<=n;i++) {          result=result*i;     }     return result; }