Bigint Calculator

A portable C++ big integer library and calculator supporting arithmetic and bitwise operations on arbitrarily large signed integers.
Implements a template Bigint<N> (where N is the bit width) and a command-line calculator for interactive use.

Features

• Bigint Template: Bigint<N> for signed integers of any bit width (e.g. 128, 256, 512).
• Arithmetic: Addition, subtraction, multiplication, division, modulo.
• Bitwise: AND, OR, XOR, NOT, bit shifts.
• Mixed-size: Operators promote operands to the larger bit width.
• Decimal I/O: Parse decimal strings and print results as decimal.
• Calculator: Interactive command-line calculator supporting expressions with +, -, *, /, %, &, |, ^, parentheses.
• No external dependencies: Uses only standard C++ headers.

Build

Open a terminal in the project folder and compile:

g++ (recommended):

g++ calculator.cpp -o calculator

MSVC (Developer Command Prompt):

cl /EHsc /std:c++17 /W4 calculator.cpp

Usage

Run the calculator:

.\calculator

Enter an expression (all on one line), e.g.:

123456789123456789 + 987654321098765432

or

(123456789123456789 * 2) ^ 42

The result will be printed in decimal.

Example

> 1000000000000000000000000000000 * 123456789
123456789000000000000000000000000
------------

API Reference

• Constructors:
  • Bigint<256> a(42);
  • Bigint<128> b("12345678901234567890");
• Operators: +, -, *, /, %, &, |, ^, <<, >>, comparisons.
• Decimal output: std::cout << a.num() << '\n';
• Bitwise: a & b, a | b, a ^ b, ~a
• Mixed-size: Bigint<256> + Bigint<128> returns Bigint<256>

Limitations

• Overflow wraps/truncates at the template bit width.
• Decimal parsing/printing is portable, but very large numbers may be slow.
• For production use, consider GMP or Boost.Multiprecision.