#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <malloc.h>
#include "lceb.h"

static char **combs;
static int ncombs=0;

void print_comb(n)
    int n;
{
    printf("comb %d/%d=[%s]\n", n, ncombs, combs[n]);
}
void print_combs()
{
    int i;
    printf("op combs: ");
    for (i=0; i<ncombs; ++i)
        printf("%s ", combs[i]);
    putchar('\n');
}
static unsigned n_combine(nops, len)
    int nops, len;
{
    int result = 1;
    while(len > 0){
        if(len & 1)
            result *= nops;
        nops *= nops;
        len >>=1;
    }
    return result;
}

static char *combine(ops, len, n)
    char *ops;                                    /* string to combine */
    int len;                                      /* len of result */
    int n;                                        /* iteration # */
{
    static char *res=NULL;
    static int len_ops;
    int i;

    if (!res) {                                   // 1st call
        len_ops=strlen(ops);
#       ifdef DEBUG_MEM
        printf("mem: allocating operators working area (%d bytes)\n", len+1);
#       endif
        res=malloc(len * sizeof(char) + 1);
    }
    for(i=0; i<len; ++i){
        res[len -i -1] = ops[n % len_ops];
        n /= len_ops;
    }
    return res;
}

void gen_combinations(nops)
    int nops;
{
    char *ops="/-*+";
    int i, n_combs;
    int len_ops=strlen(ops);
#   ifdef DEBUG_OPER
    printf("gen_combinations(%d)\n", nops);
#   endif
    n_combs=n_combine(len_ops, nops);
#   ifdef DEBUG_MEM
    printf("allocating %d operators combinations\n", n_combs);
#   endif
    combs=malloc(sizeof (char*)*n_combs);
    for (i=0; i<n_combs; ++i) {
        combs[ncombs]=strdup(combine(ops, nops, i));
        ncombs++;
    }
}

int n_combs()
{
    return ncombs;
}
char *nth_comb(n)
    int n;
{
    return combs[n];
}

#ifdef STANDALONE
int main(ac, av)
    int ac;
    char **av;
{
    char *ops="/-+*", *p;
    int len_ops=strlen(ops);
    int i, nops, ncombs;

    if (ac!=2) {
        fprintf(stderr, "usage: %s nops\n", *av);
        exit (1);
    }
    nops=atoi(*(av+1));
    ncombs=n_combine(len_ops, nops);
    combs=malloc(sizeof (char*)*ncombs);
    printf("# operators combinations : %d\nlist = ", ncombs);
    for (i=0; i<ncombs; ++i) {
        p=combine(ops, nops, i);
        printf("[%s]\n", p);
        //for (j=0; j<4; ++j)
        //    distribute(j, p);
        //printf("\n");
    }
}
#endif