| 1 | /* |
| 2 | * Matt McCutchen's Big Integer Library |
| 3 | * http://mysite.verizon.net/mccutchen/bigint/ |
| 4 | */ |
| 5 | |
| 6 | /* |
| 7 | * This sample file demonstrates the most important features of the Big Integer Library. |
| 8 | * |
| 9 | * To get started quickly with the library, imitate the code in `main' below. |
| 10 | * |
| 11 | * If you want more detail or more speed or can't find a feature here, |
| 12 | * look in the appropriate source file. This file shows only the more ``user-friendly'' features; |
| 13 | * the other features are messier but worth learning eventually. |
| 14 | * |
| 15 | * GO FORTH and play with many-digit numbers! (c.f. The TeXbook.) |
| 16 | */ |
| 17 | |
| 18 | // Standard libraries |
| 19 | #include <string> |
| 20 | #include <iostream> |
| 21 | |
| 22 | // For the BigInteger class itself. |
| 23 | #include "BigInteger.hh" |
| 24 | |
| 25 | // For the 4 routines `easy BI/BU <=> string' and `iostream' integration. |
| 26 | #include "BigIntegerUtils.hh" |
| 27 | |
| 28 | int main() { |
| 29 | try { |
| 30 | BigInteger a; // a is 0 |
| 31 | int b = 535; |
| 32 | |
| 33 | a = b; // From int to BigInteger... |
| 34 | b = a; // ...and back, no casts required! |
| 35 | /* |
| 36 | * If a were too big for an int you'd get a runtime exception. The Big Integer Library |
| 37 | * throws C-strings (that is, `const char *'s) when something goes wrong. It's a good |
| 38 | * idea to catch them; the `try/catch' construct wrapping all this code is an example |
| 39 | * of how to do this. Some C++ compilers need a special command-line option to compile |
| 40 | * code that uses exceptions. |
| 41 | */ |
| 42 | |
| 43 | BigInteger c(a); // Copy a BigInteger. |
| 44 | |
| 45 | BigInteger d(-314159265); // c is -314159265. The `int' literal is converted to a BigInteger. |
| 46 | |
| 47 | // Ahem: that's too big to be an `int' literal (or even a `long' literal)! |
| 48 | // Disillusion yourself now -- this won't compile. |
| 49 | //BigInteger e(3141592653589793238462643383279); |
| 50 | |
| 51 | std::string s("3141592653589793238462643383279"); |
| 52 | BigInteger f = easyStringToBI(s); |
| 53 | // Ah. The string is converted to a BigInteger, and strings can be as long as you want. |
| 54 | |
| 55 | std::string s2 = easyBItoString(f); // You can convert the other way too. |
| 56 | |
| 57 | std::cout << f << std::endl; // f is stringified and send to std::cout. |
| 58 | |
| 59 | /* |
| 60 | * Let's do some math! |
| 61 | * |
| 62 | * The Big Integer Library provides three kinds of operators: |
| 63 | * |
| 64 | * (1) Overloaded ``value'' operators: +, -, *, /, %, unary -. |
| 65 | * Big-integer code using these operators looks identical to |
| 66 | * code using the primitive integer types. The operator takes |
| 67 | * one or two BigInteger inputs and returns a BigInteger result, |
| 68 | * which can then be assigned to a BigInteger variable or used |
| 69 | * in an expression. |
| 70 | * |
| 71 | * (2) Overloaded assignment operators: +=, -=, *=, /=, %=, |
| 72 | * ++, --, flipSign. |
| 73 | * Again, these are used on BigIntegers just like on ints. |
| 74 | * They take one writable BigInteger that both provides an |
| 75 | * operand and receives a result. The first five also take |
| 76 | * a second read-only operand. |
| 77 | * |
| 78 | * (3) ``Put-here'' operations: `add', `subtract', etc. |
| 79 | * Use these if and only if you are concerned about performance. |
| 80 | * They require fewer BigInteger copy-constructions and assignments |
| 81 | * than do operators in (1) or (2). Most take two read-only operands |
| 82 | * and save the result in the invoked object `*this', whose previous |
| 83 | * value is irrelevant. `divideWithRemainder' is an exception. |
| 84 | * <<< NOTE >>>: Put-here operations do not return a value: they don't need to!! |
| 85 | */ |
| 86 | |
| 87 | BigInteger g(314159), h(265); |
| 88 | // All five ``value'' operators |
| 89 | std::cout << (g + h) << '\n' << (g - h) << '\n' << (g * h) |
| 90 | << '\n' << (g / h) << '\n' << (g % h) << std::endl; |
| 91 | |
| 92 | BigInteger i(5), j(10), k; |
| 93 | // These two lines do the same thing: k is set to a BigInteger containing 15. |
| 94 | k = i + j; |
| 95 | k.add(i, j); |
| 96 | |
| 97 | // Let's do some heavy lifting. |
| 98 | std::cout << "Powers of 3" << std::endl; |
| 99 | std::cout << "How many do you want?" << std::endl; |
| 100 | int maxPower; |
| 101 | std::cin >> maxPower; |
| 102 | |
| 103 | BigUnsigned x(1), three(3); |
| 104 | for (int power = 0; power <= maxPower; power++) { |
| 105 | std::cout << "3^" << power << " = " << x << std::endl; |
| 106 | x *= three; // A BigInteger assignment operator |
| 107 | } |
| 108 | |
| 109 | std::cout << "There you go. Goodbye." << std::endl; |
| 110 | |
| 111 | } catch(char const* err) { |
| 112 | std::cout << "Sorry, the library threw an exception:\n" |
| 113 | << err << std::endl; |
| 114 | } |
| 115 | |
| 116 | return 0; |
| 117 | } |
| 118 | |
| 119 | /* |
| 120 | * Here is the output of a sample run of this sample program: |
| 121 | |
| 122 | 3141592653589793238462643383279 |
| 123 | 314424 |
| 124 | 313894 |
| 125 | 83252135 |
| 126 | 1185 |
| 127 | 134 |
| 128 | Powers of 3 |
| 129 | How many do you want? |
| 130 | 2 |
| 131 | 3^0 = 1 |
| 132 | 3^1 = 3 |
| 133 | 3^2 = 9 |
| 134 | There you go. Goodbye. |
| 135 | |
| 136 | */ |