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

exprtk_simple_example_11.cpp

@@ -0,0 +1,67 @@
+/*
+ **************************************************************
+ *         C++ Mathematical Expression Toolkit Library        *
+ *                                                            *
+ * Simple Example 11                                          *
+ * Author: Arash Partow (1999-2014)                           *
+ * 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 square_wave2()
+{
+   std::string expr_string = " r := 0;                               "
+                             " for(i := 0; i < 1000; i += 1)         "
+                             " {                                     "
+                             "   r += (1/(2i+1))*sin((4i+2)*pi*f*t); "
+                             " };                                    "
+                             " r *= a*(4 / pi);                      ";
+
+   static const T pi = T(3.14159265358979323846);
+
+   T f = pi / T(10);
+   T t = T(0);
+   T a = T(10);
+
+   exprtk::symbol_table<T> symbol_table;
+   symbol_table.add_variable("f",f);
+   symbol_table.add_variable("t",t);
+   symbol_table.add_variable("a",a);
+   symbol_table.add_constants();
+
+   exprtk::expression<T> expression;
+   expression.register_symbol_table(symbol_table);
+
+   exprtk::parser<T> parser;
+   parser.enable_unknown_symbol_resolver();
+
+   parser.compile(expr_string,expression);
+
+   const T delta = (T(4) * pi) / T(1000);
+
+   for (t = (T(-2) * pi); t <= (T(+2) * pi); t += delta)
+   {
+      T result = expression.value();
+      printf("%19.15f\t%19.15f\n",t,result);
+   }
+}
+
+int main()
+{
+   square_wave2<double>();
+   return 0;
+}