README.md

Boost Matheval

Documentation Coverage

This library uses Boost.Spirit (QI for C++98 and X3 for C++14) and Boost.Fusion (and Boost.Phoenix with C++98) to parse and evaluate mathematical expressions.

The examples below use the X3 variant of Boost Matheval.

Motivating example 1

#include <iostream>
#include "matheval.hpp"

int main() {
    std::cout << matheval::parse("1+1") << '\n';
}

Outputs

2

Motivating example 2

#include <iostream>
#include <map>
#include "matheval.hpp"

int main() {
    std::map<std::string,double> symtab;
    symtab.emplace(std::make_pair("x",  2));
    symtab.emplace(std::make_pair("y", -1));
    std::cout << matheval::parse("cbrt(x/2 + sqrt(x**2/4 + y**3/24))",symtab) << '\n';
}

Outputs

1.25548

Motivating example 3

We can also evaluate an expression multiple times without paying the cost of parsing again.

#include <iostream>
#include <map>
#include "matheval.hpp"

int main() {
    matheval::Parser parser;
    parser.parse("x + 1");
    std::cout << parser.evaluate({std::make_pair("x",1)}) << ' '
              << parser.evaluate({std::make_pair("x",2)}) << '\n';
}

Outputs

2 3

Build instructions

To build Boost Matheval, just follow the usual CMake workflow.

mkdir build
cd build
cmake ..
make         # build the library and the examples
make check   # build and run the tests

Requirements and Limitations

General:

• C++14 compatible compiler, i.e. GCC >= 4.8, Clang, Visual Studio 2015.
• Boost.Spirit, Boost.Phoenix, and Boost.MathConstants.
• No support for ternary functions (e.g. if).
• No support for complex numbers.

Alternatives

• GNU libmatheval is a C library built using the parser generator YACC with about the same scope as Boost Matheval.
• ExprTk is a true monster with almost 40000 lines in a single header file. It implements a complete state machine including things like logical operations, control structures, and even file IO. Compilation time is even longer than with Boost Matheval.

License

Distributed under the Boost Software License, Version 1.0.