Question

So I’m practicing pointers to functions, and tried out making this simple program, here’s a snippet of it. It still gives me an error “invalid lvalue” when it comes to assigning the address. funcptr = &addnum for example. Also I can’t help but wonder what’s the use of this? Isn’t it much simpler to call the function? Or am I misunderstanding something

#include <stdio.h>
int arithnum(int base);
int addnum(int base,int new);
int subnum(int base,int new);
int mulnum(int base,int new);
int divnum(int base,int new);
typedef int *ptrdef(int,int);
int arithnum(int base)
{
    char operator;
    int operand;
    ptrdef funcptr;
    printf("Enter operator: ");
    scanf("\n%c",&operator);
    printf("Enter second operand: ");
    scanf("%d",&operand);
    switch(operator)
    {
        case '+':
            funcptr = &addnum;
            break;
        case '-':
            funcptr = &subnum;
            break;
        case '*':
            funcptr = &mulnum;
            break;
        case '/':
            funcptr = &divnum;
            break;
    }
    return funcptr(base,operand);
}

Answer 1

ITYM

typedef int (*ptrdef)(int,int);

as your version is a function which returns an int * while you want a function pointer which returns an int.

---

Just a hint: I know that the following is not common sense, but I prefer to typedef the function itself and then do

typedef int myfunc(int,int);
myfunc therealfunction; // bites me if I do a mistake
int therealfunction(int a, int b)
{
    // do stuff and
    return 42;
}
myfunc * funcptr = &therealfunction;

in order to get bitten by an error instead of a warning if I accidentally change the declaration of therealfunction.