Add ExprTk_BUILD_EXAMPLES to build examples

Also move examples into an examples folder

examples/exprtk_simple_example_07.cpp

@@ -0,0 +1,70 @@
+/*
+ **************************************************************
+ *         C++ Mathematical Expression Toolkit Library        *
+ *                                                            *
+ * Simple Example 7                                           *
+ * Author: Arash Partow (1999-2023)                           *
+ * URL: https://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 MIT License.                   *
+ * https://www.opensource.org/licenses/MIT                    *
+ *                                                            *
+ **************************************************************
+*/
+
+
+#include <cstdio>
+#include <string>
+
+#include "exprtk.hpp"
+
+template <typename T>
+void logic()
+{
+   typedef exprtk::symbol_table<T> symbol_table_t;
+   typedef exprtk::expression<T>   expression_t;
+   typedef exprtk::parser<T>       parser_t;
+
+   const std::string expression_string = "not(A and B) or C";
+
+   symbol_table_t symbol_table;
+   symbol_table.create_variable("A");
+   symbol_table.create_variable("B");
+   symbol_table.create_variable("C");
+
+   expression_t expression;
+   expression.register_symbol_table(symbol_table);
+
+   parser_t parser;
+   parser.compile(expression_string,expression);
+
+   printf(" # | A | B | C | %s\n"
+          "---+---+---+---+-%s\n",
+          expression_string.c_str(),
+          std::string(expression_string.size(),'-').c_str());
+
+   for (int i = 0; i < 8; ++i)
+   {
+      symbol_table.get_variable("A")->ref() = T((i & 0x01) ? 1 : 0);
+      symbol_table.get_variable("B")->ref() = T((i & 0x02) ? 1 : 0);
+      symbol_table.get_variable("C")->ref() = T((i & 0x04) ? 1 : 0);
+
+      const int result = static_cast<int>(expression.value());
+
+      printf(" %d | %d | %d | %d | %d \n",
+             i,
+             static_cast<int>(symbol_table.get_variable("A")->value()),
+             static_cast<int>(symbol_table.get_variable("B")->value()),
+             static_cast<int>(symbol_table.get_variable("C")->value()),
+             result);
+   }
+}
+
+int main()
+{
+   logic<double>();
+   return 0;
+}