This header only library provides interface for parsing mathematical functions of one variable.
Library itself is (one) header only, so the easiest way is just putting it into your project. However, it depends on lexy parsing library. Author of lexy suggests adding following lines to cmake to make everything work.
include(FetchContent)
FetchContent_Declare(lexy URL https://lexy.foonathan.net/download/lexy-src.zip)
FetchContent_MakeAvailable(lexy)
target_link_libraries(project_name foonathan::lexy)To use this library you only have to include function_parser.hpp in
your project.
#include <az_math/function_parser.hpp>Having library include, expression parsing can be done by using
function parse_expression which takes int as an argument and returns
std::shared_ptr to abstract class az::Production. If parsing
doesn't generate value, nullptr is returned.
std::string expr = /*string expression*/;
std::shared_ptr<az::Production> function = az::parse_expression(expr);
if (!function) {
// rise error...
} else {
// do something...
}Production interface provides function evaluate to calculating
obtained function value for given x.
double x = 3.14;
double value = function->evaluate(x);Library parses expressions based on positive decimal numbers and
x variable. This atoms can be merged using following operators:
+ - * / ^.
Negative value is possible to obtain by using - operator, e.g.
-3.14.
There is also possibility to use some of the basic math functions using
expression function_kw(x). Library supports this function keywords:
sin- calculates sine,cos- calculates cosine,tan- calculates tangent,cot- calculates cotangent,sqrt- calculates square root,cbrt- calculates cube root.ln- calculates natural logarithm.log- calculates base 10 logarithm.lg- calculates base 2 logarithm.arcsin- calculates arcsine.arccos- calculates arccosine.arctan- calculates arctangent.
Operation order is preserved and brackets are supported to force operation order. Example:
std::string expr = "6/3*(x+1)";
std::shared_ptr<az::Production> function = az::parse_expression(expr);
function->evaluate(2); // will be evaluated as ((6/3)*(2+1))->(2*3)->(6)