/** delimiter.c -- by James D. Lin (last updated: 2006-05-29)
  *
  *     Demonstration of a hack to print delimiters only between items
  *     in a sequence with minimal code duplication and without using
  *     an extra conditional per iteration.
  */

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


/** Returns the length of an array; array must be a true array, not a pointer. */
#define ARRAY_LENGTH(array) (sizeof (array) / sizeof (array)[0])


int main(void)
{
    const char* words[]
        = { "the", "five", "boxing", "wizards", "jump", "quickly" };
    const char* delimiter = "_";

    size_t i = 0;
    size_t n = ARRAY_LENGTH(words);

    /* Conventional approach #1:
     * Handle the first element explicitly as a special case before
     * starting the loop. (Or alternatively, handle the last element
     * explicitly after exiting the loop.)
     *
     * Duplicates the meat of the loop body.
     */
    i = 0;
    if (i < n)
    {
        while (i < n - 1)
        {
            printf("%s", words[i]);
            printf("%s", delimiter);
            i++;
        }
        printf("%s", words[i]);
        putchar('\n');
    }

    /* Conventional approach #2:
     * Handle the first (or alternatively, the last) element explicitly as
     * a special case inside the loop.
     *
     * Compact but evaluates two conditionals per iteration.
     */
    i = 0;
    while (i < n)
    {
        printf("%s", words[i]);
        i++;
        if (i != n) { printf("%s", delimiter); }
    }
    putchar('\n');

    /* Conventional approach #3:
     * Remove the redundant outer conditional from approach #2.
     *
     * Slightly less compact, and control flow is slightly less clear.
     */
    i = 0;
    if (i < n)
    {
        while (1)
        {
            printf("%s", words[i]);
            ++i;
            if (i == n) { break; }
            printf("%s", delimiter);
        }
    }
    putchar('\n');

    /* Hacky approach:
     * Special-case the first iteration, but don't do it inside the loop,
     * and avoid duplicating code.
     *
     * Uses 'goto', which most people are afraid to use.  Code is relatively
     * compact but weird-looking.
     */
    i = 0;
    if (i < n)
    {
        goto start;
        while (i < n)
        {
            printf("%s", delimiter);
        start:
            printf("%s", words[i]);
            i++;
        }
    }
    putchar('\n');

    return EXIT_SUCCESS;
}