Start a set of simple examples.

* examples/calc++/Makefile, examples/calc++/calc++-driver.cc,
* examples/calc++/calc++-driver.hh,
* examples/calc++/calc++-parser.yy,
* examples/calc++/calc++-scanner.ll, examples/calc++/calc++.cc,
* examples/calc++/compile, examples/calc++/test: New.

examples/calc++/calc++-driver.hh

@@ -0,0 +1,64 @@
+#ifndef CALCXX_DRIVER_HH
+# define CALCXX_DRIVER_HH
+# include <string>
+# include <map>
+
+/// Forward declarations.
+union YYSTYPE;
+
+namespace yy
+{
+  class calcxx_parser;
+  class location;
+}
+
+class calcxx_driver;
+
+// Announce to Flex the prototype we want for lexing function, ...
+# define YY_DECL						\
+  int yylex (YYSTYPE* yylval, yy::location* yylloc, calcxx_driver& driver)
+// ... and declare it for the parser's sake.
+YY_DECL;
+
+/// Conducting the whole scanning and parsing of Calc++.
+class calcxx_driver
+{
+public:
+  calcxx_driver ();
+  virtual ~calcxx_driver ();
+
+  /// The variables.
+  std::map<std::string, int> variables;
+
+  /// \name Handling the scanner.
+  /// \{
+  /// Open \a file for scanning.
+  void scan_begin ();
+  /// End scanning, clean up memory.
+  void scan_end ();
+  /// Whether to enable scanner traces.
+  bool trace_scanning;
+  /// \}
+
+  /// \name Handling the parser.
+  /// \{
+  /// Parse the file \a f.
+  void parse (const std::string& f);
+  /// The file being parsed.
+  std::string file;
+  /// Whether to enable parsing traces.
+  bool trace_parsing;
+  /// \}
+
+  /// The result.
+  int result;
+
+  /// \name Error handling.
+  /// \{
+  /// Register a located error.
+  void error (const yy::location& l, const std::string& m);
+  /// Register an error.
+  void error (const std::string& m);
+  /// \}
+};
+#endif