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Comments on What does a variable followed by parentheses ("ptr()") mean?
Parent
What does a variable followed by parentheses ("ptr()") mean?
What does ptr() mean in this code?
#include<stdio.h>
#include<stdlib.h>
void PrintHello()
{
printf("Hello\n");
}
int Add(int a, int b)
{
return a+b;
}
int main ()
{
void (*ptr)();
ptr = PrintHello;
ptr(); //For this specific line of code, what does it mean?
}
Post
void (*ptr)() defines a function pointer. It says that ptr is a pointer to a function. But that function must have a void return type, and take an arbitrary number of parameters (that's what the empty parentheses defines).
Then, ptr = PrintHello assigns the PrintHello function to the ptr pointer (and it works because PrintHello matches the signature: it has a void return type). So, now ptr is pointing to PrintHello.
Finally, ptr() is calling the function that ptr points to (in this case, PrintHello). It has the same effect as calling PrintHello(), and the parentheses are needed because it's a function call. But the function takes no parameters, thus the empty parentheses.
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