C++ Mathematical Expression Library (ExprTk) http://www.partow.net/programming/exprtk/index.html

exprtk_simple_example_01.cpp

@@ -29,6 +29,7 @@ void trig_function()
    typedef exprtk::parser<T>             parser_t;
 
    std::string expression_string = "clamp(-1.0,sin(2 * pi * x) + cos(x / 2 * pi),+1.0)";
+
    T x;
 
    symbol_table_t symbol_table;