--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/absyntax/visitor.hh	Wed Jan 31 15:32:38 2007 +0100
@@ -0,0 +1,171 @@
+/*
+ * (c) 2003 Mario de Sousa
+ *
+ * Offered to the public under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * This code is made available on the understanding that it will not be
+ * used in safety-critical situations without a full and competent review.
+ */
+
+/*
+ * An IEC 61131-3 IL and ST compiler.
+ *
+ * Based on the
+ * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)
+ *
+ */
+
+
+/*
+ * VISITOR.HH
+ *
+ *
+ * The asbract syntax tree is scaned several times
+ * during the whole compilation process. For e.g., stage 3 verifies
+ * semantics, and stage 4 produces output.
+ *
+ * Since the number of functions that need to scan through
+ * the abtract syntax tree may increase in time, (e.g. new
+ * output formats, new semantic checks, etc...) while the
+ * abstract syntax tree class structure is pretty stable
+ * (i.e. the ST and IL languages will not be changing much...),
+ * we use the 'visitor' design patern.
+ *
+ * It is not strictly necessary to use this pattern, but it does
+ * have the advantage of bringing together the functions
+ * that implement the same algorithm, each on a different
+ * class of object in the abstract syntax tree.
+ *
+ *
+ * This file contains the interface that each visitor class
+ * must implement in order to be able to visit the abstract
+ * syntax tree (class visitor_c)
+ *
+ * Three implementations of this interface are also provided,
+ * that may be later extended to execute a particular algorithm.
+ *
+ * The null (class null_visitor_c) does nothing.
+ *
+ * The iterator (class iterator_visitor_c) iterates through
+ * every object in the syntax tree.
+ *
+ * The search class (class search_visitor_c) iterates through
+ * every object, until one returns a value != NULL.
+ */
+
+
+#ifndef _VISITOR_HH
+#define _VISITOR_HH
+
+
+
+
+#include "absyntax.hh"
+
+
+
+#define SYM_LIST(class_name_c)	\
+  virtual void *visit(class_name_c *symbol) = 0;
+
+#define SYM_TOKEN(class_name_c)	\
+  virtual void *visit(class_name_c *symbol) = 0;
+
+#define SYM_REF0(class_name_c)	\
+  virtual void *visit(class_name_c *symbol) = 0;
+
+#define SYM_REF2(class_name_c, ref1, ref2)	\
+  virtual void *visit(class_name_c *symbol) = 0;
+
+#define SYM_REF4(class_name_c, ref1, ref2, ref3, ref4)	\
+  virtual void *visit(class_name_c *symbol) = 0;
+
+#define SYM_REF6(class_name_c, ref1, ref2, ref3, ref4, ref5, ref6)	\
+  virtual void *visit(class_name_c *symbol) = 0;
+
+class visitor_c {
+  public:
+  #include "absyntax.def"
+
+  virtual ~visitor_c(void);
+};
+
+#undef SYM_LIST
+#undef SYM_TOKEN
+#undef SYM_REF0
+#undef SYM_REF2
+#undef SYM_REF4
+#undef SYM_REF6
+
+
+
+
+
+
+#define SYM_LIST(class_name_c)	\
+  virtual void *visit(class_name_c *symbol);
+
+#define SYM_TOKEN(class_name_c)	\
+  virtual void *visit(class_name_c *symbol);
+
+#define SYM_REF0(class_name_c)	\
+  virtual void *visit(class_name_c *symbol);
+
+#define SYM_REF2(class_name_c, ref1, ref2)	\
+  virtual void *visit(class_name_c *symbol);
+
+#define SYM_REF4(class_name_c, ref1, ref2, ref3, ref4)	\
+  virtual void *visit(class_name_c *symbol);
+
+#define SYM_REF6(class_name_c, ref1, ref2, ref3, ref4, ref5, ref6)	\
+  virtual void *visit(class_name_c *symbol);
+
+
+
+
+
+class null_visitor_c: public visitor_c {
+  public:
+  #include "absyntax.def"
+
+  virtual ~null_visitor_c(void);
+};
+
+
+
+class iterator_visitor_c: public visitor_c {
+  protected:
+  void *visit_list(list_c *list);
+
+  public:
+  #include "absyntax.def"
+
+  virtual ~iterator_visitor_c(void);
+};
+
+
+class search_visitor_c: public visitor_c {
+  protected:
+  void *visit_list(list_c *list);
+
+  public:
+  #include "absyntax.def"
+
+  virtual ~search_visitor_c(void);
+};
+
+
+#undef SYM_LIST
+#undef SYM_TOKEN
+#undef SYM_REF0
+#undef SYM_REF2
+#undef SYM_REF4
+#undef SYM_REF6
+
+#endif /*  _VISITOR_HH */