C isn't that hard: void ( *( *f[] ) () ) ()

Question

I just saw a picture today and think I\'d appreciate explanations. So here is the picture:

I found this confusing and wondered if such codes are ever prac

Answer 1

In C, declaration mirrors usage—that’s how it’s defined in the standard. The declaration:

void (*(*f[])())()

Is an assertion that the expression (*(*f[i])())() produces a result of type void. Which means:

• f must be an array, since you can index it:

  f[i]
  

• The elements of f must be pointers, since you can dereference them:

  *f[i]
  

• Those pointers must be pointers to functions taking no arguments, since you can call them:

  (*f[i])()
  

• The results of those functions must also be pointers, since you can dereference them:

  *(*f[i])()
  

• Those pointers must also be pointers to functions taking no arguments, since you can call them:

  (*(*f[i])())()
  

• Those function pointers must return void

The “spiral rule” is just a mnemonic that provides a different way of understanding the same thing.