Thread: Typedef

>What is Foo here...
A pointer to a function that takes no arguments and returns a value of type int.

>i have used typedef but not like this..
Then follow the same rules you use to figure out any typedef:

Code:

typedef int foo_t;

A typedef uses the same syntax as a variable declaration, except instead of creating a variable with the specified name, it creates a type synonym with the specified name. So in the above typedef, foo_t is a synonym for int. Now let's declare a pointer to a function:

Code:

#include <stdio.h>

int do_something(void)
{
  puts("foo");
}

int main()
{
  int (*foo)(void);

  foo = &do_something;
  foo();

  return 0;
}

That's tedious, so instead of declaring the pointer type directly, make it a typedef:

Code:

#include <stdio.h>

typedef int (*foo_t)(void);

int do_something(void)
{
  puts("foo");
}

int main()
{
  foo_t foo;

  foo = &do_something;
  foo();

  return 0;
}

Problem solved as long as you recognize the type being typedef'd.