X-Git-Url: https://mattmccutchen.net/bigint/bigint.git/blobdiff_plain/e257a1b25b880dc6246189e7ede1d0ea3db6337d..cb2f0c288d4b7acfa37d7a9c8bc1024c3f332b5f:/sample.cc diff --git a/sample.cc b/sample.cc index a9e4d46..62b41df 100644 --- a/sample.cc +++ b/sample.cc @@ -1,137 +1,100 @@ -/* -* Matt McCutchen's Big Integer Library -* http://mysite.verizon.net/mccutchen/bigint/ -*/ - -/* -* This sample file demonstrates the most important features of the Big Integer Library. -* -* To get started quickly with the library, imitate the code in `main' below. -* -* If you want more detail or more speed or can't find a feature here, -* look in the appropriate source file. This file shows only the more ``user-friendly'' features; -* the other features are messier but worth learning eventually. -* -* GO FORTH and play with many-digit numbers! (c.f. The TeXbook.) -*/ +// Sample program demonstrating the use of the Big Integer Library. // Standard libraries #include #include -// For the BigInteger class itself. -#include "BigInteger.hh" - -// For the 4 routines `easy BI/BU <=> string' and `iostream' integration. -#include "BigIntegerUtils.hh" +// `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; - - a = b; // From int to BigInteger... - b = a; // ...and back, no casts required! - /* - * If a were too big for an int you'd get a runtime exception. The Big Integer Library - * throws C-strings (that is, `const char *'s) when something goes wrong. It's a good - * idea to catch them; the `try/catch' construct wrapping all this code is an example - * of how to do this. Some C++ compilers need a special command-line option to compile - * code that uses exceptions. - */ - + + /* 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. - - std::cout << "here 0" << std::endl; - - BigInteger d(-314159265); // c is -314159265. The `int' literal is converted to a BigInteger. - - // Ahem: that's too big to be an `int' literal (or even a `long' literal)! - // Disillusion yourself now -- this won't compile. + + // 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); - - std::cout << "here 1" << std::endl; - + + // Instead you can convert the number from a string. std::string s("3141592653589793238462643383279"); - BigInteger f = easyStringToBI(s); - // Ah. The string is converted to a BigInteger, and strings can be as long as you want. - - std::cout << "here 2" << std::endl; - - std::string s2 = easyBItoString(f); // You can convert the other way too. - - std::cout << "here 3" << std::endl; - - std::cout << f << std::endl; // f is stringified and send to std::cout. - - std::cout << "here 4" << std::endl; - - /* - * Let's do some math! - * - * The Big Integer Library provides three kinds of operators: - * - * (1) Overloaded ``value'' operators: +, -, *, /, %, unary -. - * Big-integer code using these operators looks identical to - * code using the primitive integer types. The operator takes - * one or two BigInteger inputs and returns a BigInteger result, - * which can then be assigned to a BigInteger variable or used - * in an expression. - * - * (2) Overloaded assignment operators: +=, -=, *=, /=, %=, - * ++, --, flipSign. - * Again, these are used on BigIntegers just like on ints. - * They take one writable BigInteger that both provides an - * operand and receives a result. The first five also take - * a second read-only operand. - * - * (3) ``Put-here'' operations: `add', `subtract', etc. - * Use these if and only if you are concerned about performance. - * They require fewer BigInteger copy-constructions and assignments - * than do operators in (1) or (2). Most take two read-only operands - * and save the result in the invoked object `*this', whose previous - * value is irrelevant. `divideWithRemainder' is an exception. - * <<< NOTE >>>: Put-here operations do not return a value: they don't need to!! - */ - + 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); - // All five ``value'' operators - std::cout << (g + h) << '\n' << (g - h) << '\n' << (g * h) - << '\n' << (g / h) << '\n' << (g % h) << std::endl; - - std::cout << "here 5" << std::endl; - - BigInteger i(5), j(10), k; - // These two lines do the same thing: k is set to a BigInteger containing 15. - k = i + j; - k.add(i, j); - - std::cout << "here 6" << std::endl; - - // Let's do some heavy lifting. - std::cout << "Powers of 3" << std::endl; - std::cout << "How many do you want?" << std::endl; - int maxPower; - std::cin >> maxPower; - - BigUnsigned x(1), three(3); + 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 << "3^" << power << " = " << x << std::endl; - x *= three; // A BigInteger assignment operator + std::cout << "314^" << power << " = " << x << std::endl; + x *= big314; // A BigInteger assignment operator } - - std::cout << "There you go. Goodbye." << std::endl; - + + // 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 << "Sorry, the library threw an exception:\n" + std::cout << "The library threw an exception:\n" << err << std::endl; } - + return 0; } /* -* Here is the output of a sample run of this sample program: +The original sample program produces this output: 3141592653589793238462643383279 314424 @@ -139,12 +102,24 @@ int main() { 83252135 1185 134 -Powers of 3 -How many do you want? -2 -3^0 = 1 -3^1 = 3 -3^2 = 9 -There you go. Goodbye. +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 */