07.例子

        /*
     * Determine if the sky is blue by checking that it isn't night.
     * CAVEAT: Only sometimes right.  May return TRUE when the answer
     * is FALSE.  Consider clouds, eclipses, short days.
     * NOTE: Uses 'hour' from 'hightime.c'.  Returns 'int' for
     * compatibility with the old version.
     */
    int                /* true or false */
    skyblue()
    {
        extern int    hour;        /* current hour of the day */

        return (hour >= MORNING && hour <= EVENING);
    }

    /*
     * Find the last element in the linked list
     * pointed to by nodep and return a pointer to it.
     * Return NULL if there is no last element.
     */
    node_t *
    tail(nodep)
    node_t    *nodep;            /* pointer to head of list */
    {
        register node_t    *np;        /* advances to NULL */
        register node_t    *lp;        /* follows one behind np */

        if (nodep == NULL)
            return (NULL);
        for (np = lp = nodep; np != NULL; lp = np, np = np->next)
            ;    /* VOID */
        return (lp);
    }