sample.cc

Go to the documentation of this file.

// Sample program demonstrating the use of the Big Integer Library.

// Standard libraries
#include <string>
#include <iostream>

// `BigIntegerLibrary.hh' includes all of the library headers.
#include "BigIntegerLibrary.hh"

int main() {
    /* The library throws `const char *' error messages when things go
     * wrong.  It's a good idea to catch them using a `try' block like this
     * one.  Your C++ compiler might need a command-line option to compile
     * code that uses exceptions. */
    try {
        BigInteger a; // a is 0
        int b = 535;

        /* Any primitive integer can be converted implicitly to a
         * BigInteger. */
        a = b;

        /* The reverse conversion requires a method call (implicit
         * conversions were previously supported but caused trouble).
         * If a were too big for an int, the library would throw an
         * exception. */
        b = a.toInt();

        BigInteger c(a); // Copy a BigInteger.

        // The int literal is converted to a BigInteger.
        BigInteger d(-314159265);

        /* This won't compile (at least on 32-bit machines) because the
         * number is too big to be a primitive integer literal, and
         * there's no such thing as a BigInteger literal. */
        //BigInteger e(3141592653589793238462643383279);

        // Instead you can convert the number from a string.
        std::string s("3141592653589793238462643383279");
        BigInteger f = stringToBigInteger(s);

        // You can convert the other way too.
        std::string s2 = bigIntegerToString(f); 

        // f is implicitly stringified and sent to std::cout.
        std::cout << f << std::endl;

        /* Let's do some math!  The library overloads most of the
         * mathematical operators (including assignment operators) to
         * work on BigIntegers.  There are also ``copy-less''
         * operations; see `BigUnsigned.hh' for details. */

        // Arithmetic operators
        BigInteger g(314159), h(265);
        std::cout << (g + h) << '\n'
            << (g - h) << '\n'
            << (g * h) << '\n'
            << (g / h) << '\n'
            << (g % h) << std::endl;

        // Bitwise operators
        BigUnsigned i(0xFF0000FF), j(0x0000FFFF);
        // The library's << operator recognizes base flags.
        std::cout.flags(std::ios::hex | std::ios::showbase);
        std::cout << (i & j) << '\n'
            << (i | j) << '\n'
            << (i ^ j) << '\n'
            // Shift distances are ordinary unsigned ints.
            << (j << 21) << '\n'
            << (j >> 10) << '\n';
        std::cout.flags(std::ios::dec);

        // Let's do some heavy lifting and calculate powers of 314.
        int maxPower = 10;
        BigUnsigned x(1), big314(314);
        for (int power = 0; power <= maxPower; power++) {
            std::cout << "314^" << power << " = " << x << std::endl;
            x *= big314; // A BigInteger assignment operator
        }

        // Some big-integer algorithms (albeit on small integers).
        std::cout << gcd(BigUnsigned(60), 72) << '\n'
            << modinv(BigUnsigned(7), 11) << '\n'
            << modexp(BigUnsigned(314), 159, 2653) << std::endl;

        // Add your own code here to experiment with the library.
    } catch(char const* err) {
        std::cout << "The library threw an exception:\n"
            << err << std::endl;
    }

    return 0;
}

/*
The original sample program produces this output:

3141592653589793238462643383279
314424
313894
83252135
1185
134
0xFF
0xFF00FFFF
0xFF00FF00
0x1FFFE00000
0x3F
314^0 = 1
314^1 = 314
314^2 = 98596
314^3 = 30959144
314^4 = 9721171216
314^5 = 3052447761824
314^6 = 958468597212736
314^7 = 300959139524799104
314^8 = 94501169810786918656
314^9 = 29673367320587092457984
314^10 = 9317437338664347031806976
12
8
1931

*/