A Big Integer Class for C++

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This is a Big Integer Class, implemented in C++, for handling very large numbers, or numbers greater than unsigned long long int in a 64 bit implementation. So, it can easily operate on numbers greater than 10^18.

Usage

Just include the file as a preprocessor directive, like : #include "name" where name denotes your filename, the name you saved for this Big Int file. Also, ensure that you keep it in the same directory as your working file, else you have to write the complete path in that place.

1. Download the BigInt.cpp source file. Then #include it in your code:

   #include "BigInt.cpp"   // the actual path may vary

2. Create objects of the BigInt class, and do what you got to do!

   BigInt big1 = 1234567890, big2;
   big2 = "9876543210123456789098765432101234567890";
   
   std::cout << big1 * big2 * 123456 << "\n";
   // Output: 1505331490682966620443288524512589666204282352096057600

Features

Operators

• Assignment: =

  The second operand can either be a BigInt, an integer (up to long long) or a string (std::string or a string literal).

  big1 = 1234567890;
  big1 = "123456789012345678901234567890";
  big1 = big2;

• Unary arithmetic: +, -

  big1 = +big2;   // doesn't return the absolute value
  big1 = -big2;

• Binary arithmetic: +, -, *, /, %

  One of the operands has to be a BigInt and the other can be a BigInt, an integer (up to long long) or a string (std::string or a string literal).

  big1 = big2 + 1234567890;
  big1 = big2 - "123456789012345678901234567890";
  big1 = big2 * big3;
  big1 = 1234567890 / big2;
  big1 = "123456789012345678901234567890" % big2;

• Arithmetic-assignment: +=, -=, *=, /=, %=

  The second operand can either be a BigInt, an integer (up to long long) or a string (std::string or a string literal).

  big1 += big2;
  big1 -= 1234567890;
  big1 *= "123456789012345678901234567890";
  big1 /= big2;
  big1 %= 1234567890;

• Increment and decrement: ++, --

  big1 = ++big2;   // pre-increment
  big1 = --big2;   // pre-decrement
  
  big1 = big2++;   // post-increment
  big1 = big2--;   // post-decrement

• Relational: <, >, <=, >=, ==, !=

  One of the operands has to be a BigInt and the other can be a BigInt, an integer (up to long long) or a string (std::string or a string literal).

  if (big1 < 1234567890
      or big1 > "123456789012345678901234567890"
      or big1 <= big2
      or 1234567890 >= big1
      or "123456789012345678901234567890" == big1
      or big1 != big3) {
      ...
  }

• I/O stream: <<, >>

  std::cout << big1 << ", " << big2 << "\n";
  output_file << big1 << ", " << big2 << "\n";
  
  std::cin >> big1 >> big2;
  input_file >> big1 >> big2;

Functions

• Conversion: to_string, to_int, to_long, to_long_long

  Convert a BigInt to either a string, int, long, or long long.

  Note: If the BigInt is beyond the range of the target type, an [out_of_range exception][out_of_range-exception] is thrown.

  std::string str = big1.to_string();
  
  int var = big1.to_int();
  
  long var = big1.to_long();
  
  long long var = big1.to_long_long();

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Note: We are new to c++. We just created this class for only our learning purposes. We want to improve more in the future. We've tried our best for bug-free writing code, so any kind of mistake pointers there would be appreciated as well.

Thanks in advance for pointing us to any kind of mistake.

Credit

This Big Integer class was created by Farid Islam and Sujon Hasan