Namaran

memo_square.c

#include <stdio.h>

typedef int (*compute_fn)(int);

static int calls = 0;

int square(int n) {
    calls++;
    return n * n;
}

typedef struct {
    compute_fn compute;
    int cache[16];
    unsigned char cached[16];
} memo_t;

int memo_get(memo_t *m, int n) {
    if (!m->cached[n]) {
        m->cache[n] = m->compute(n);
        m->cached[n] = 1;
    }
    return m->cache[n];
}

int main(void) {
    memo_t m = { .compute = square };
    printf("%d\n", memo_get(&m, 4));
    printf("%d\n", memo_get(&m, 4));
    printf("%d\n", memo_get(&m, 5));
    printf("calls=%d\n", calls);
}