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closure.c
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closure.c
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#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
typedef struct List list_t;
struct List
{
void *head;
list_t *tail;
};
list_t *makelist(void *x, list_t *xs)
{
list_t *ans = (list_t *)malloc(sizeof(list_t));
ans->head = x;
ans->tail = xs;
return ans;
}
list_t *map(void *(*f)(void *, void *), void *env, list_t *xs)
{
if (xs == NULL)
return NULL;
return makelist(f(env, xs->head), map(f, env, xs->tail));
}
list_t *filter(bool (*f)(void *, void *), void *env, list_t *xs)
{
if (xs == NULL)
return NULL;
if (f(env, xs->head))
return makelist(xs->head, filter(f, env, xs->tail));
return filter(f, env, xs->tail);
}
int length(list_t *xs)
{
int ans = 0;
while (xs != NULL)
{
++ans;
xs = xs->tail;
}
return ans;
}
void *doubleInt(void *ignore, void *i)
{
return (void *)(((intptr_t)i) * 2);
}
// assumes list holds intptr_t fileds
list_t *doubleAll(list_t *xs)
{
return map(doubleInt, NULL, xs);
}
// type casts to match what filter expects
bool isN(void *n, void *i)
{
return ((intptr_t)n) == ((intptr_t)i);
}
int countNs(list_t *xs, intptr_t n)
{
return length(filter(isN, (void *)n, xs));
}