runtime.c

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

#define num_shift 2
#define num_mask 0b11
#define num_tag 0b00

#define bool_shift 7
#define bool_mask 0b1111111
#define bool_tag 0b0011111

#define heap_mask 0b111
#define pair_tag 0b010
#define fn_tag 0b110

extern int64_t entry(void *heap);

void error()
{
    printf("ERROR");
    exit(1);
}

uint64_t read_num()
{
    int r = 0;
    scanf("%d", &r);
    return r << num_shift;
}

void print_newline()
{
    printf("\n");
}

void print_value(uint64_t value)
{
    if ((value & num_mask) == num_tag)
    {
        int64_t ivalue = (int64_t)value;
        printf("%" PRIi64, ivalue >> num_shift);
    }
    else if ((value & bool_mask) == bool_tag)
    {
        if (value >> bool_shift)
        {
            printf("true");
        }
        else
        {
            printf("false");
        }
    }
    else if ((value & heap_mask) == pair_tag)
    {
        uint64_t v1 = *(uint64_t *)(value - pair_tag);
        uint64_t v2 = *(uint64_t *)(value - pair_tag + 8);
        printf("(pair ");
        print_value(v1);
        printf(" ");
        print_value(v2);
        printf(")");
    }
    else if ((value & heap_mask) == fn_tag)
    {
        printf("<function>");
    }
    else
    {
        printf("BAD VALUE %" PRIu64, value);
    }
}

int main(int argc, char **argv)
{
    entry((void *)malloc(4096));
    return 0;
}