quesgen.c

/*
 * quesgen.c - Math question generator for elementary school pupils
 * Copyright (c) 2014 Maxthon Chan <xcvista@me.com>
 *
 * Compiling this program: Use your preferred C99 compiler. clang/LLVM is
 * preferred, GCC is acceptable, MSVC is not guaranteed to work.
 *     clang quesgen.c -std=c99 -o quesgen
 * No special library other than standard C library is required.
 *
 * Using this program:
 *     ./quesgen [count] > output.txt
 * By default, it generates 100 questions.
 *
 * License:
 *
 * You are allowed to use, modify, copy and distribute this software, as long as
 * you:
 *     1) Keep the copyright notice, this license and the following disclaimer
 *        in your modified and/or distributed source code,
 *     2) Keep the copyright notice, this license and the following disclaimer
 *        with your modified and/or distributed binary code.
 *     3) Not claim your modified version of this program a work of its original
 *        author(s) unless explicitedly allowed.
 *
 * Disclaimer:
 *
 * THIS SOFTWARE IS PROVIDED TO YOU ON THE "AS-IS" BASIS. NO WARRANTY WHATSOEVER
 * IS PROVIDED OR GUARANTEED FROM THE AUTHORS OF THIS SOFTWARE, INCLUDING BUT
 * NOT LIMITED TO SUITABILITY OF MERCHANT, ABILITY TO SUPPORT CRITICAL SYSTEMS
 * OR ANY SPECIFIC USE CASE. YOU ARE USING THIS SOFTWARE AT YOUR OWN RISK. WE
 * AUTHORS TRY OUR BEST TO PREVENT PERCIEVEABLE ISSUES IN THIS SOFTWARE, BUT
 * WE CANNOT GUARANTEE IT IS ERROR-FREE.
 */

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

int main(int argc, char *const *argv)
{
    int count = 100;
    
    int a, b, sym;

    if (argc > 1) // Handle the sole argument, if exists.
    {
        count = atoi(argv[1]);
    }
    
    if (count <= 0) // Handle bad argument...
    {
        count = 100; // ... by ignoring it.
    }
    
    srand(time(NULL)); // Initialize PRNG.
    
    for (int i = 0; i < count; i++)
    {
        sym = rand() & 0x3; // Generate the symbol. Faster this way.
        
        if (sym == 3) // Division is handled differently.
        {
            a = rand() % 30 + 1;
            b = rand() % 30 + 1;
            printf("%d / %d =\n", a * b, b);
        }
        else // Other three is trivial.
        {
            static const char syms[] = "+-*"; // Faster this way.
            a = rand() % 100 + 1;
            b = rand() % 100 + 1;
            printf("%d %c %d =\n", a, syms[sym], b);
        }
    }
    
    return EXIT_SUCCESS;
}