Go back to Richel Bilderbeek's homepage.

Go back to Richel Bilderbeek's C++ page.

 

 

 

 

 

(C++) BigInt Hello BigInt

 

'Hello BigInt' is like a 'Hello World' program, except for additionally using the BigInt library.

 

Running Hello BigInt depends on your operating system or system environment:

 

 

The code of Hello BigInt is the sample code given by BigInt's author on the BigInt website. This code is shown below.

 

 

 

 

 

 

// 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
*/

 

 

 

 

 

External links

 

 

 

 

 

 

Go back to Richel Bilderbeek's C++ page.

Go back to Richel Bilderbeek's homepage.

 

Valid XHTML 1.0 Strict