Binary package “libfparser4” in ubuntu focal

Function Parser for C++

 This C++ library offers a class which can be used to parse and evaluate a
 mathematical function from a string (which might be eg. requested from the
 user).
 .
 The syntax of the function string is similar to mathematical expressions
 written in C/C++ (the exact syntax is specified in the documentation below).
 The function can then be evaluated with different values of variables.