How to understand this define

Question

Nowadays , i was reading the APUE.and i found the function defined as below:

void (*signal(int signo, void (*func)(int)))(int);

i was confused,

Answer 1

void (*signal(int signo, void (*func)(int)))(int);

signal is function that takes int and a pointer to function taking int and returning void and returns a function pointer taking int and returning void. That is,

typedef void(*funcPtr)(int)

then we have

funcPtr signal(int signo, funcPtr func); //equivalent to the above

The syntax is indeed strange, and such things better be done with a typedef. As an example, if you want to declare a function that takes an int and returns a pointer to a function taking char and returning double will be

double (*f(int))(char);

Edit: after a comment that reads "Wooooooow", I am providing another example which is more "woooow" :)

Let's declare a function that takes
1. a pointer to array of 5 pointers to functions each taking float and returning double.
2. a pointer to array of 3 ponters to arrays of 4 ints
and returns a pointer to function that takes a pointer to function taking int and returning a pointer to function taking float and returning void and returns unsigned int.

The typedef solution would be this:

typedef double (*f1ptr) (float);
typedef f1ptr (*arr1ptr)[5];
typedef int (*arr2ptr)[4];
typedef arr2ptr (*arr3ptr)[3];
typedef void(*f2Ptr)(float);
typedef f2ptr (*f3ptr)(int);
typedef unsigned int (*f4ptr) (f3ptr);
f4ptr TheFunction(arr1ptr arg1, arr3ptr arg2);

Now, the funny part :) Without typedefs this will be:

 unsigned int (*TheFunction( double (*(*)[5])(float), int(*(*)[3])[4]))( void(*(*)(int))(float))

My god, did I just write that? :)