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

exprtk_simple_example_06.cpp

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+/*
+ **************************************************************
+ *         C++ Mathematical Expression Toolkit Library        *
+ *                                                            *
+ * Simple Example 6                                           *
+ * 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 vector_function()
+{
+   typedef exprtk::expression<T> expression_t;
+   std::string expression_string = "z := (3sin(x) + 2log(y))";
+
+   const std::size_t vec_size = 5;
+
+   T x[vec_size] = { T(1.1), T(2.2), T(3.3), T(4.4), T(5.5) };
+   T y[vec_size] = { T(1.1), T(2.2), T(3.3), T(4.4), T(5.5) };
+   T z[vec_size] = { T(0.0), T(0.0), T(0.0), T(0.0), T(0.0) };
+
+   T x_ = x[0];
+   T y_ = y[0];
+   T z_ = z[0];
+
+   exprtk::symbol_table<T> symbol_table;
+   symbol_table.add_variable("x",x_);
+   symbol_table.add_variable("y",y_);
+   symbol_table.add_variable("z",z_);
+
+   expression_t expression;
+   expression.register_symbol_table(symbol_table);
+
+   exprtk::parser<T> parser;
+   parser.compile(expression_string,expression);
+
+   for (std::size_t i = 0; i < vec_size; ++i)
+   {
+      x_ = x[i]; y_ = y[i]; z_ = z[i];
+      expression.value();
+      x[i] = x_; y[i] = y_; z[i] = z_;
+   }
+}
+
+int main()
+{
+   vector_function<double>();
+   return 0;
+}