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

exprtk_simple_example_01.cpp

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+/*
+ **************************************************************
+ *         C++ Mathematical Expression Toolkit Library        *
+ *                                                            *
+ * Simple Example 1                                           *
+ * Author: Arash Partow (1999-2013)                           *
+ * URL: http://www.partow.net/programming/exprtk/index.html   *
+ *                                                            *
+ * Copyright notice:                                          *
+ * Free use of the Mathematical Expression Toolkit Library is *
+ * permitted under the guidelines and in accordance with the  *
+ * most current version of the Common Public License.         *
+ * http://www.opensource.org/licenses/cpl1.0.php              *
+ *                                                            *
+ **************************************************************
+*/
+
+
+#include <cstdio>
+#include <string>
+#include "exprtk.hpp"
+
+
+template<typename T>
+void trig_function()
+{
+   std::string expression_string = "clamp(-1.0,sin(2 * pi * x) + cos(x / 2 * pi),+1.0)";
+   T x;
+   exprtk::symbol_table<T> symbol_table;
+   symbol_table.add_variable("x",x);
+   symbol_table.add_constants();
+
+   exprtk::expression<T> expression;
+   expression.register_symbol_table(symbol_table);
+
+   exprtk::parser<T> parser;
+   parser.compile(expression_string,expression);
+
+   for (x = T(-5.0); x <= T(+5.0); x += 0.001)
+   {
+      T y = expression.value();
+      printf("%19.15f\t%19.15f\n",x,y);
+   }
+}
+
+int main()
+{
+   trig_function<double>();
+   return 0;
+}