doj / boost_matheval

Evaluate mathematical expressions using Boost.Spirit

Boost Matheval

This library uses Boost.Spirit (QI for C++11 and X3 for C++14) and Boost.Fusion (and Boost.Phoenix with C++11) to parse and evaluate mathematical expressions.

Examples

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

Documentation

cd build
cmake ..
make doxygen
open doc/doxygen/html/index.html

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 operators (?:).
• No support for complex numbers.

doj fork

this repository was forked from https://github.com/hmenke/boost_matheval

Changes from the upstream version:

• use C++11 for the QI parser
• QI and X3 parser support the same mathematical functions.
• use C++ exceptions to abort processing if a mathematical function uses an invalid parameter. All exceptions thrown by the matheval library are derived from matheval::exception . See the matheval.hpp header file for details.
• add ifelse() function

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.