func.h

/*
   $----------------$
   | Example usage: |
   $----------------$------------------------------------------------------$
   | #include <stdbool.h>                                                  |
   | #include <stdio.h>                                                    |
   |                                                                       |
   | #include "func.h"                                                     |
   |                                                                       |
   | LIST_TYPE(int)                                                        |
   |                                                                       |
   | bool is_even(const int *x)                                            |
   | { return                                                              |
   |         *x % 2 == 0;                                                  |
   | }                                                                     |
   |                                                                       |
   | int *print_int(const int *x)                                          |
   | { return int_dup((                                                    |
   |         printf("%d\n", *x), x));                                      |
   | }                                                                     |
   |                                                                       |
   | int main(void)                                                        |
   | {                                                                     |
   |         let intList* list = list(int, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10); |
   |         let intList* filtered_list = int_filter(list, is_even);       |
   |         int_map(filtered_list, print_int);                            |
   | }                                                                     |
   $-----------------------------------------------------------------------$
*/

#ifndef FUNC_H__
#define FUNC_H__

#include <stdbool.h>
#include <stdlib.h>
#include <string.h>

#define let const

#define list(type, ...) list__(type, ((type[]){ __VA_ARGS__ }))

#define list__(type, arr) \
	type##_list__(sizeof(arr[0]), sizeof(arr) / sizeof(arr[0]), arr)

#define LIST_TYPE(type) \
typedef bool type##Predicate(const type *); \
typedef type *type##UnaryFunc(const type *); \
typedef type *type##BinaryFunc(const type *, const type *); \
\
typedef struct type##list type##List; \
\
struct type##list { \
	type *head; \
	type##List *tail; \
}; \
\
type *type##_dup(const type *t); \
type##List *type##_list__(const size_t size, const size_t nmemb, \
		const type arr[]); \
type##List *type##_prepend(type *head, type##List *tail); \
type##List *type##_map(const type##List *list, type##UnaryFunc *func); \
type##List *type##_filter(const type##List *list, type##Predicate *func); \
type *type##_reduce(const type##List *list, type##BinaryFunc *func); \
\
inline type *type##_dup(const type *t) \
{ return \
	memcpy(malloc(sizeof(type)), t, sizeof(type)); \
} \
\
inline type##List *type##_list__(const size_t size, const size_t nmemb, \
		const type arr[]) \
{ return \
	nmemb == 0 \
	? NULL \
	: type##_prepend(type##_dup(arr), \
		type##_list__(size, nmemb - 1, arr + 1)); \
} \
\
inline type##List *type##_prepend(type *head, type##List *tail) \
{ \
	type##List * const super = malloc(sizeof(type##List)); \
	super->head = head; \
	super->tail = tail; \
	return super; \
} \
\
inline type##List *type##_map(const type##List *list, type##UnaryFunc *func) \
{ return \
	list == NULL \
	? NULL \
	: type##_prepend(func(list->head), type##_map(list->tail, func)); \
} \
\
inline type##List *type##_filter(const type##List *list, type##Predicate *func) \
{ return \
	list == NULL \
	? NULL \
	: func(list->head) \
		? type##_prepend(list->head, type##_filter(list->tail, func)) \
		: type##_filter(list->tail, func); \
} \
\
inline type *type##_reduce(const type##List *list, type##BinaryFunc *func) \
{ return \
	list->tail == NULL \
	? list->head \
	: func(list->head, type##_reduce(list->tail, func)); \
}

#endif