1 /*

     2  * (c) 2003 Mario de Sousa

     3  *

     4  * Offered to the public under the terms of the GNU General Public License

     5  * as published by the Free Software Foundation; either version 2 of the

     6  * License, or (at your option) any later version.

     7  *

     8  * This program is distributed in the hope that it will be useful, but

     9  * WITHOUT ANY WARRANTY; without even the implied warranty of

    10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General

    11  * Public License for more details.

    12  *

    13  * This code is made available on the understanding that it will not be

    14  * used in safety-critical situations without a full and competent review.

    15  */

    16 

    17 /*

    18  * An IEC 61131-3 IL and ST compiler.

    19  *

    20  * Based on the

    21  * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)

    22  *

    23  */

    24 

    25 

    26 /*

    27  * VISITOR.HH

    28  *

    29  *

    30  * The asbract syntax tree is scaned several times

    31  * during the whole compilation process. For e.g., stage 3 verifies

    32  * semantics, and stage 4 produces output.

    33  *

    34  * Since the number of functions that need to scan through

    35  * the abtract syntax tree may increase in time, (e.g. new

    36  * output formats, new semantic checks, etc...) while the

    37  * abstract syntax tree class structure is pretty stable

    38  * (i.e. the ST and IL languages will not be changing much...),

    39  * we use the 'visitor' design patern.

    40  *

    41  * It is not strictly necessary to use this pattern, but it does

    42  * have the advantage of bringing together the functions

    43  * that implement the same algorithm, each on a different

    44  * class of object in the abstract syntax tree.

    45  *

    46  *

    47  * This file contains the interface that each visitor class

    48  * must implement in order to be able to visit the abstract

    49  * syntax tree (class visitor_c)

    50  *

    51  * Three implementations of this interface are also provided,

    52  * that may be later extended to execute a particular algorithm.

    53  *

    54  * The null (class null_visitor_c) does nothing.

    55  *

    56  * The iterator (class iterator_visitor_c) iterates through

    57  * every object in the syntax tree.

    58  *

    59  * The search class (class search_visitor_c) iterates through

    60  * every object, until one returns a value != NULL.

    61  */

    62 

    63 

    64 #ifndef _VISITOR_HH

    65 #define _VISITOR_HH

    66 

    67 

    68 

    69 

    70 #include "absyntax.hh"

    71 

    72 

    73 

    74 #define SYM_LIST(class_name_c)	\

    75   virtual void *visit(class_name_c *symbol) = 0;

    76 

    77 #define SYM_TOKEN(class_name_c)	\

    78   virtual void *visit(class_name_c *symbol) = 0;

    79 

    80 #define SYM_REF0(class_name_c)	\

    81   virtual void *visit(class_name_c *symbol) = 0;

    82 

    83 #define SYM_REF2(class_name_c, ref1, ref2)	\

    84   virtual void *visit(class_name_c *symbol) = 0;

    85 

    86 #define SYM_REF4(class_name_c, ref1, ref2, ref3, ref4)	\

    87   virtual void *visit(class_name_c *symbol) = 0;

    88 

    89 #define SYM_REF6(class_name_c, ref1, ref2, ref3, ref4, ref5, ref6)	\

    90   virtual void *visit(class_name_c *symbol) = 0;

    91 

    92 class visitor_c {

    93   public:

    94   #include "absyntax.def"

    95 

    96   virtual ~visitor_c(void);

    97 };

    98 

    99 #undef SYM_LIST

   100 #undef SYM_TOKEN

   101 #undef SYM_REF0

   102 #undef SYM_REF2

   103 #undef SYM_REF4

   104 #undef SYM_REF6

   105 

   106 

   107 

   108 

   109 

   110 

   111 #define SYM_LIST(class_name_c)	\

   112   virtual void *visit(class_name_c *symbol);

   113 

   114 #define SYM_TOKEN(class_name_c)	\

   115   virtual void *visit(class_name_c *symbol);

   116 

   117 #define SYM_REF0(class_name_c)	\

   118   virtual void *visit(class_name_c *symbol);

   119 

   120 #define SYM_REF2(class_name_c, ref1, ref2)	\

   121   virtual void *visit(class_name_c *symbol);

   122 

   123 #define SYM_REF4(class_name_c, ref1, ref2, ref3, ref4)	\

   124   virtual void *visit(class_name_c *symbol);

   125 

   126 #define SYM_REF6(class_name_c, ref1, ref2, ref3, ref4, ref5, ref6)	\

   127   virtual void *visit(class_name_c *symbol);

   128 

   129 

   130 

   131 

   132 

   133 class null_visitor_c: public visitor_c {

   134   public:

   135   #include "absyntax.def"

   136 

   137   virtual ~null_visitor_c(void);

   138 };

   139 

   140 

   141 

   142 class iterator_visitor_c: public visitor_c {

   143   protected:

   144   void *visit_list(list_c *list);

   145 

   146   public:

   147   #include "absyntax.def"

   148 

   149   virtual ~iterator_visitor_c(void);

   150 };

   151 

   152 

   153 class search_visitor_c: public visitor_c {

   154   protected:

   155   void *visit_list(list_c *list);

   156 

   157   public:

   158   #include "absyntax.def"

   159 

   160   virtual ~search_visitor_c(void);

   161 };

   162 

   163 

   164 #undef SYM_LIST

   165 #undef SYM_TOKEN

   166 #undef SYM_REF0

   167 #undef SYM_REF2

   168 #undef SYM_REF4

   169 #undef SYM_REF6

   170 

   171 #endif /*  _VISITOR_HH */