Something useful about function pointers in C.
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# include <stdio.h> | |
# include <stddef.h> | |
// x: A function taking short and returning char. | |
char x (short); // Usage: char c = x ('H'); | |
// x (); // A function | |
// x (short); // taking short | |
// char x (short); // and returning char. | |
// y: A pointer to a function taking short and returning char. | |
char (* y) (short); // Usage: char c = (* y) ('E'); | |
// * y; // A pointer | |
// (* y) (); // to a function | |
// (* y) (short); // taking short | |
// char (* y) (short); // and returning char. | |
// // Array: char (* arr [COUNT]) (short); | |
// // Array usage: (* arr [index]) ('A'); | |
// z: A function taking two ints and returning pointer | |
// to a function taking short and returning char. | |
char (* z (int, int)) (short); // Usage: char c = (* z (1, 2)) ('L'); | |
// z () // A function | |
// z (int, int) // taking two ints | |
// * z (int, int) // and returning pointer | |
// (* z (int, int)) () // to a function | |
// (* z (int, int)) (short) // taking short | |
// char (* z (int, int)) (short) // and returning char. | |
// w: A pointer to a function taking two ints and returning | |
// pointer to a function taking short and returning char. | |
char (* (* w) (int, int)) (short); // Usage: char c = (* (* w) (1, 2)) ('L'); | |
// * w; // A pointer | |
// (* w) (); // to a function | |
// (* w) (int, int); // taking two ints | |
// * (* w) (int, int); // and returning pointer | |
// (* (* w) (int, int)) (); // to a function | |
// (* (* w) (int, int)) (short); // taking short | |
// char (* (* w) (int, int)) (short) // and returning char. | |
// // Array: char (* (* arr [COUNT]) (int, int)) (short); | |
// // Array usage: (* (* arr [index]) (1, 2)) ('B'); | |
char * (* (* a (long, long, long)) (int, int)) (short); | |
char * (* (* (* b) (long, long, long)) (int, int)) (short); | |
char * (* (* (* c (double, double, double, double)) (long, long, long)) (int, int)) (short); | |
char * (* (* (* (* d) (double, double, double, double)) (long, long, long)) (int, int)) (short); | |
char * (* (* (* (* e (char, char, char, char, char)) (double, double, double, double)) (long, long, long)) (int, int)) (short); | |
char * (* (* (* (* (* f) (char, char, char, char, char)) (double, double, double, double)) (long, long, long)) (int, int)) (short); | |
// Typedefs | |
typedef char X (short); // Usage: X _x; // For function definitions only. | |
typedef char (* Y) (short); // Usage: Y _y = & x; | |
// // Array: Y _yy [COUNT]; | |
typedef char (* Z (int, int)) (short); // Usage: Z _z; // For function definitions only. | |
typedef char (* (* W) (int, int)) (short); // Usage: W _w = & z; | |
// // Array: W _ww [COUNT]; | |
char x (short a) { return (char) a; } | |
char (* z (int a, int b)) (short) { return & x; } | |
# define NL() putchar ('\n') | |
int main (void) | |
{ | |
y = & x; | |
w = & z; | |
putchar (x ('H')); | |
NL (); | |
putchar ((* y) ('E')); | |
NL (); | |
putchar ((* z (1, 2)) ('L')); | |
NL (); | |
putchar ((* (* w) (1, 2)) ('L')); | |
NL (); | |
puts (":D"); | |
// char (* yy [5]) (short) = {& x, & x, & x, & x, & x}; | |
// char (* (* ww [5]) (int, int)) (short) = {& z, & z, & z, & z, & z}; | |
Y yy [5] = {& x, & x, & x, & x, & x}; | |
W ww [5] = {& z, & z, & z, & z, & z}; | |
for (size_t i = 0; i < 5; i++) | |
putchar ((* yy [i]) ('A')); | |
NL (); | |
for (size_t i = 0; i < 5; i ++) | |
putchar ((* (* ww [i]) (1, 2)) ('B')); | |
NL (); | |
} |
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