Abusing the C preprocessor a bit

quickslice.h

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

#define QUICKSLICE(SLICETYPE, SLICENAME) \
typedef struct SLICENAME { \
	unsigned int len, cap; \
	SLICETYPE *data; \
} SLICENAME; \
typedef SLICETYPE (SLICENAME ## _mapper) (SLICETYPE); \
typedef char (SLICENAME ## _folder) (SLICETYPE); \
SLICENAME SLICENAME ## _create (int cap) { \
	SLICENAME s; \
	s.len = 0; \
	s.cap = cap; \
	s.data = (SLICETYPE *)malloc(sizeof(SLICETYPE) * cap); \
	return s; \
} \
void SLICENAME ## _append (SLICENAME *s, SLICETYPE v) { \
	if (s->len >= s->cap) \
		s->data = (SLICETYPE *)realloc(s->data, sizeof(SLICETYPE) * (s->cap *= 2)); \
	s->data[s->len++] = v; \
} \
void SLICENAME ## _remove (SLICENAME *s, int index) { \
	if (index < s->len) { \
		memcpy(s->data + index, s->data + index + 1, sizeof(SLICETYPE) * (s->len - (index + 1))); \
		s->len--; \
	} \
} \
void SLICENAME ## _free (SLICENAME *s) { \
	free((void *)s->data); \
	s->len = s->cap = 0; \
	s->data = NULL; \
} \
void SLICENAME ## _map (SLICENAME s, SLICENAME ## _mapper f) { \
	int i; \
	for (i = 0; i < s.len; i++) \
		s.data[i] = f(s.data[i]); \
} \
SLICENAME SLICENAME ## _fold (SLICENAME s, SLICENAME ## _folder f) { \
	int i; \
	SLICENAME n = SLICENAME ## _create(s.len); \
	for (i = 0; i < s.len; i++) \
		if (f(s.data[i])) \
			SLICENAME ## _append(&n, s.data[i]); \
	return n; \
}

test.c

#include <stdio.h>
#include "quickslice.h"

QUICKSLICE(int, ints)
QUICKSLICE(char *, strings);

int power2(int x) {
	return 1 << x;
}

char notW(char *s) {
	return s[0] != 'W';
}

int main() {
	int i;
	ints list = ints_create(5);
	strings words = strings_create(5);
	strings words2;
	for (i = 0; i < 20; i++)
		ints_append(&list, i);
	ints_map(list, power2);
	strings_append(&words, "Hello");
	strings_append(&words, "Bonjour");
	strings_append(&words, "Wilkommen");
	strings_append(&words, "Buenos dias");
	words2 = strings_fold(words, notW);
	for (i = 0; i < list.len; i++)
		printf("2 ** %d = %d\n", i, list.data[i]);
	for (i = 0; i < words2.len; i++)
		printf("%s\n", words2.data[i]);
	ints_free(&list);
	strings_free(&words);
	strings_free(&words2);
}