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++/Makefile

@@ -0,0 +1,15 @@
+all: calc++
+
+calc++:
+	flex -ocalc++-scanner.cc calc++-scanner.ll
+	bison -o calc++-parser.cc calc++-parser.yy
+	$(CC) -o calc++ calc++.cc calc++-driver.cc calc++-parser.cc calc++-scanner.cc
+
+check: all
+	./test
+
+clean:
+	rm -f *~ *.o *.tab.* input position.hh location.hh stack.hh \
+	      calc++-parser.cc calc++-parser.hh \
+	      calc++-scanner.cc \
+	      calc++

examples/calc++/calc++-driver.cc

@@ -0,0 +1,37 @@
+#include "calc++-driver.hh"
+#include "calc++-parser.hh"
+
+calcxx_driver::calcxx_driver ()
+  : trace_scanning (false),
+    trace_parsing (false)
+{
+  variables["one"] = 1;
+  variables["two"] = 2;
+}
+
+calcxx_driver::~calcxx_driver ()
+{
+}
+
+void
+calcxx_driver::parse (const std::string &f)
+{
+  file = f;
+  scan_begin ();
+  yy::calcxx_parser parser (*this);
+  parser.set_debug_level (trace_parsing);
+  parser.parse ();
+  scan_end ();
+}
+
+void
+calcxx_driver::error (const yy::location& l, const std::string& m)
+{
+  std::cerr << l << ": " << m << std::endl;
+}
+
+void
+calcxx_driver::error (const std::string& m)
+{
+  std::cerr << m << std::endl;
+}

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

examples/calc++/calc++-parser.yy

@@ -0,0 +1,68 @@
+%skeleton "lalr1.cc"                                  /*  -*- C++ -*- */
+%define "parser_class_name" "calcxx_parser"
+%defines
+%{
+# include <string>
+# include "calc++-driver.hh"
+%}
+
+%error-verbose
+
+// The parsing context.
+%parse-param { calcxx_driver& driver }
+%lex-param   { calcxx_driver& driver }
+
+%locations
+%initial-action
+{
+  // Initialize the initial location.
+  @$.begin.filename = @$.end.filename = &driver.file;
+};
+
+// Define yydebug.
+%debug
+
+// Symbols.
+
+%union
+{
+  /// Value of a numeric literal.
+  int          ival;
+  /// Name of a variable.
+  std::string *sval;
+};
+
+%token        YYEOF          0 "end of file"
+%token        TOKEN_ASSIGN     ":="
+%token <sval> TOKEN_IDENTIFIER "identifier"
+%token <ival> TOKEN_NUMBER     "number"
+%type  <ival> exp              "expression"
+
+%printer    { debug_stream () << *$$; } "identifier"
+%destructor { delete $$; } "identifier"
+
+%printer    { debug_stream () << $$; } "number" "expression"
+
+%%
+%start unit;
+unit: assignments exp  { driver.result = $2; };
+
+assignments: assignments assignment {}
+           | /* Nothing. */         {};
+
+assignment: TOKEN_IDENTIFIER ":=" exp { driver.variables[*$1] = $3; };
+
+%left '+' '-';
+%left '*' '/';
+exp: exp '+' exp   { $$ = $1 + $3; }
+   | exp '-' exp   { $$ = $1 - $3; }
+   | exp '*' exp   { $$ = $1 * $3; }
+   | exp '/' exp   { $$ = $1 / $3; }
+   | TOKEN_IDENTIFIER  { $$ = driver.variables[*$1]; }
+   | TOKEN_NUMBER      { $$ = $1; };
+%%
+void
+yy::calcxx_parser::error (const location& l, const std::string& m)
+{
+  driver.error (l, m);
+}

examples/calc++/calc++-scanner.ll

@@ -0,0 +1,45 @@
+%{                                                            /* -*- C++ -*- */
+
+# include <string>
+# include <cerrno>
+# include "calc++-driver.hh"
+# include "calc++-parser.hh"
+%}
+
+%option noyywrap nounput debug batch
+
+id    [a-zA-Z][a-zA-Z_0-9]*
+int   [0-9]+
+blank [ \t]
+
+%%
+
+%{
+# define YY_USER_ACTION  yylloc->columns (yyleng);
+  yylloc->step ();
+%}
+{blank}+   yylloc->step ();
+[\n]+      yylloc->lines (yyleng); yylloc->step ();
+
+
+[-+*/]     return yytext[0];
+":="       return TOKEN_ASSIGN;
+{int}      yylval->ival = atoi (yytext); return TOKEN_NUMBER;
+{id}       yylval->sval = new std::string (yytext); return TOKEN_IDENTIFIER;
+.          driver.error (*yylloc, "invalid character");
+
+%%
+
+void
+calcxx_driver::scan_begin ()
+{
+  yy_flex_debug = trace_scanning;
+  if (!(yyin = fopen (file.c_str (), "r")))
+    error (std::string ("cannot open ") + file);
+}
+
+void
+calcxx_driver::scan_end ()
+{
+  fclose (yyin);
+}

examples/calc++/calc++.cc

@@ -0,0 +1,18 @@
+#include <iostream>
+#include "calc++-driver.hh"
+
+int
+main (int argc, const char* argv[])
+{
+  calcxx_driver driver;
+  for (++argv; argv[0]; ++argv)
+    if (*argv == std::string ("-p"))
+      driver.trace_parsing = true;
+    else if (*argv == std::string ("-s"))
+      driver.trace_scanning = true;
+    else
+      {
+	driver.parse (*argv);
+	std::cout << driver.result << std::endl;
+      }
+}

examples/calc++/compile

@@ -0,0 +1,9 @@
+#! /bin/sh
+
+set -ex
+BISON_PKGDATADIR=$HOME/src/bison/data
+export BISON_PKGDATADIR
+
+flex -ocalc++-scanner.cc calc++-scanner.ll
+bison -o calc++-parser.cc calc++-parser.yy
+g++ -o calc++ calc++.cc calc++-driver.cc calc++-parser.cc calc++-scanner.cc

examples/calc++/test

@@ -0,0 +1,26 @@
+#! /bin/sh
+set +e
+cat >input <<EOF
+a := 1
+b := 2
+c := 3
+d := a + b * c
+d
+EOF
+
+./calc++ input
+./calc++ -p input
+
+cat >input <<EOF
+a := 1
+d := a + b * c
+EOF
+./calc++ input
+
+set -x
+echo toto
+cat >input <<EOF
+toto := 1
+toto
+EOF
+./calc++ -s input