inhowe / calculator

C++ operator precedence parser

calculator

calculator.hpp is a header-only C++ library for parsing and evaluating integer arithmetic expressions e.g. "10 * (7 - 1)". It compiles with any C++ compiler and works with any integer type e.g. int, long, uint64_t.

calculator is a simple but fast operator-precedence parser.

Supported operators

calculator.hpp uses the same operator precedence and associativity as the C++ programming language and also supports the power operator.

Operator	Description
|	Bitwise Inclusive OR
^	Bitwise Exclusive OR
&	Bitwise AND
~	Unary Complement
<<	Shift Left
>>	Shift Right
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Modulo
**	Raise to power

C++ API

Functions defined in calculator.hpp.

int calculator::eval(const std::string& expression);

template <typename T>
T calculator::eval<T>(const std::string& expression);

How to use it

calculator::eval("1+2") takes a string with an integer arithmetic expression as an argument, evaluates the arithmetic expression and returns the result. If the expression string is not a valid integer arithmetic expression a calculator::error exception is thrown.

#include "calculator.hpp"
#include <stdint.h>
#include <iostream>

int main()
{
    try
    {
        int result = calculator::eval("(0 + ~(255 & 1000)*3) / -2");
        std::cout << result << std::endl;
    
        // 64-bit arithmetic
        int64_t r64 = calculator::eval<int64_t>("2**60");
        std::cout << r64 << std::endl;
    }
    catch (calculator::error& e)
    {
        std::cerr << e.what() << std::endl;
    }

    return 0;
}