Who cares about functional programming?(thomasbandt.com)

    #include <stdio.h>
    #include <stdlib.h>

    struct generator_state {
        int next_value;
        int limit;
    };

    struct generator_state *enum_from_to(int from, int to) {
        struct generator_state *generator = malloc(sizeof *generator);
        generator->next_value = from;
        generator->limit = to;
        return generator;
    }

    int has_next(struct generator_state *state) {
        return state->next_value <= state->limit;
    }

    int next(struct generator_state *state) {
        return state->next_value++;
    }

    int main(void) {
        printf("try to enumerate from 1 to 10\n");
        struct generator_state *generator = enum_from_to(1, 10);
        while (has_next(generator)) {
            printf("%d\n", next(generator));
        }
        return 0;
    }