absyntax_utils/type_initial_value.hh
changeset 181 38d6eb056260
child 257 90782e241346
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/absyntax_utils/type_initial_value.hh	Mon Jun 01 21:08:44 2009 +0200
@@ -0,0 +1,262 @@
+/*
+ * (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)
+ *
+ */
+
+
+/*
+ * Determine the default initial value of a type declaration.
+ *
+ * This is part of the 4th stage that generates
+ * a c++ source program equivalent to the IL and ST
+ * code.
+ */
+
+/* Given a type definition declration, determine its default
+ * initial value. Note that types based on other types
+ * may have to iterate through each type it is based on
+ * to determine the initial value.
+ * E.g.
+ *  TYPE
+ *    A_t : INT := 10;
+ *    B_t : A_t := 20;
+ *    C_t : B_t;
+ *    D_t : C_t := 40;
+ *  END_TYPE
+ * Where the default initial value for C_t is 20!
+ */
+/* NOTE: The main program only needs one instance of
+ *       this class of object. This class
+ *       is therefore a singleton.
+ */
+
+class type_initial_value_c : public null_visitor_c {
+
+  private:
+    static type_initial_value_c *_instance;
+    /* constants for the default values of elementary data types... */
+    static real_c		*real_0;
+    static integer_c		*integer_0, *integer_1;
+    static boolean_literal_c	*bool_0;
+    static date_literal_c	*date_literal_0;
+    static daytime_c		*daytime_literal_0;
+    static duration_c		*time_0;
+    static date_c		*date_0;
+    static time_of_day_c	*tod_0;
+    static date_and_time_c	*dt_0;
+    static single_byte_character_string_c *string_0;
+    static double_byte_character_string_c *wstring_0;
+
+  public:
+    static type_initial_value_c *instance(void);
+
+  protected:
+    type_initial_value_c(void);
+
+  public:
+    symbol_c *get(identifier_c *type_name);
+
+
+  private:
+    void *handle_type_spec(symbol_c *base_type_name, symbol_c *type_spec_init);
+
+  private:
+    void *visit(identifier_c *type_name);
+
+    /***********************************/
+    /* B 1.3.1 - Elementary Data Types */
+    /***********************************/
+    void *visit(time_type_name_c *symbol);
+    void *visit(bool_type_name_c *symbol);
+    void *visit(sint_type_name_c *symbol);
+    void *visit(int_type_name_c *symbol);
+    void *visit(dint_type_name_c *symbol);
+    void *visit(lint_type_name_c *symbol);
+    void *visit(usint_type_name_c *symbol);
+    void *visit(uint_type_name_c *symbol);
+    void *visit(udint_type_name_c *symbol);
+    void *visit(ulint_type_name_c *symbol);
+    void *visit(real_type_name_c *symbol);
+    void *visit(lreal_type_name_c *symbol);
+    void *visit(date_type_name_c *symbol);
+    void *visit(tod_type_name_c *symbol);
+    void *visit(dt_type_name_c *symbol);
+    void *visit(byte_type_name_c *symbol);
+    void *visit(word_type_name_c *symbol);
+    void *visit(dword_type_name_c *symbol);
+    void *visit(lword_type_name_c *symbol);
+    void *visit(string_type_name_c *symbol);
+    void *visit(wstring_type_name_c *symbol);
+
+    /********************************/
+    /* B 1.3.3 - Derived data types */
+    /********************************/
+    /*  simple_type_name ':' simple_spec_init */
+    void *visit(simple_type_declaration_c *symbol);
+
+    /* simple_specification ASSIGN constant */
+    void *visit(simple_spec_init_c *symbol);
+
+    /*  subrange_type_name ':' subrange_spec_init */
+    void *visit(subrange_type_declaration_c *symbol);
+
+    /* subrange_specification ASSIGN signed_integer */
+    void *visit(subrange_spec_init_c *symbol);
+
+    /*  integer_type_name '(' subrange')' */
+    void *visit(subrange_specification_c *symbol);
+
+    /*  signed_integer DOTDOT signed_integer */
+    void *visit(subrange_c *symbol);
+
+    /*  enumerated_type_name ':' enumerated_spec_init */
+    void *visit(enumerated_type_declaration_c *symbol);
+
+    /* enumerated_specification ASSIGN enumerated_value */
+    void *visit(enumerated_spec_init_c *symbol);
+
+    /* helper symbol for enumerated_specification->enumerated_spec_init */
+    /* enumerated_value_list ',' enumerated_value */
+    void *visit(enumerated_value_list_c *symbol);
+
+    /* enumerated_type_name '#' identifier */
+    // SYM_REF2(enumerated_value_c, type, value)
+    void *visit(enumerated_value_c *symbol);
+
+    /*  identifier ':' array_spec_init */
+    void *visit(array_type_declaration_c *symbol);
+
+    /* array_specification [ASSIGN array_initialization} */
+    /* array_initialization may be NULL ! */
+    void *visit(array_spec_init_c *symbol);
+
+    /* ARRAY '[' array_subrange_list ']' OF non_generic_type_name */
+    void *visit(array_specification_c *symbol);
+
+    /* helper symbol for array_specification */
+    /* array_subrange_list ',' subrange */
+    void *visit(array_subrange_list_c *symbol);
+
+    /* array_initialization:  '[' array_initial_elements_list ']' */
+    /* helper symbol for array_initialization */
+    /* array_initial_elements_list ',' array_initial_elements */
+    void *visit(array_initial_elements_list_c *symbol);
+
+    /* integer '(' [array_initial_element] ')' */
+    /* array_initial_element may be NULL ! */
+    void *visit(array_initial_elements_c *symbol);
+    
+    /*  structure_type_name ':' structure_specification */
+    void *visit(structure_type_declaration_c *symbol);
+
+    /* structure_type_name ASSIGN structure_initialization */
+    /* structure_initialization may be NULL ! */
+    void *visit(initialized_structure_c *symbol);
+     
+    /* helper symbol for structure_declaration */
+    /* structure_declaration:  STRUCT structure_element_declaration_list END_STRUCT */
+    /* structure_element_declaration_list structure_element_declaration ';' */
+    void *visit(structure_element_declaration_list_c *symbol);
+    
+    /*  structure_element_name ':' *_spec_init */
+    void *visit(structure_element_declaration_c *symbol);
+    
+    /* helper symbol for structure_initialization */
+    /* structure_initialization: '(' structure_element_initialization_list ')' */
+    /* structure_element_initialization_list ',' structure_element_initialization */
+    void *visit(structure_element_initialization_list_c *symbol);
+    
+    /*  structure_element_name ASSIGN value */
+    void *visit(structure_element_initialization_c *symbol);
+    
+    /*  string_type_name ':' elementary_string_type_name string_type_declaration_size string_type_declaration_init */
+    /*
+     * NOTE:
+     * (Summary: Contrary to what is expected, the
+     *           string_type_declaration_c is not used to store
+     *           simple string type declarations that do not include
+     *           size limits.
+     *           For e.g.:
+     *             str1_type: STRING := "hello!"
+     *           will be stored in a simple_type_declaration_c
+     *           instead of a string_type_declaration_c.
+     *           The following:
+     *             str2_type: STRING [64] := "hello!"
+     *           will be stored in a sring_type_declaration_c
+     *
+     *           Read on for why this is done...
+     * End Summary)
+     *
+     * According to the spec, the valid construct
+     * TYPE new_str_type : STRING := "hello!"; END_TYPE
+     * has two possible routes to type_declaration...
+     *
+     * Route 1:
+     * type_declaration: single_element_type_declaration
+     * single_element_type_declaration: simple_type_declaration
+     * simple_type_declaration: identifier ':' simple_spec_init
+     * simple_spec_init: simple_specification ASSIGN constant
+     * (shift:  identifier <- 'new_str_type')
+     * simple_specification: elementary_type_name
+     * elementary_type_name: STRING
+     * (shift: elementary_type_name <- STRING)
+     * (reduce: simple_specification <- elementary_type_name)
+     * (shift: constant <- "hello!")
+     * (reduce: simple_spec_init: simple_specification ASSIGN constant)
+     * (reduce: ...)
+     *
+     *
+     * Route 2:
+     * type_declaration: string_type_declaration
+     * string_type_declaration: identifier ':' elementary_string_type_name string_type_declaration_size string_type_declaration_init
+     * (shift:  identifier <- 'new_str_type')
+     * elementary_string_type_name: STRING
+     * (shift: elementary_string_type_name <- STRING)
+     * (shift: string_type_declaration_size <-  empty )
+     * string_type_declaration_init: ASSIGN character_string
+     * (shift: character_string <- "hello!")
+     * (reduce: string_type_declaration_init <- ASSIGN character_string)
+     * (reduce: string_type_declaration <- identifier ':' elementary_string_type_name string_type_declaration_size string_type_declaration_init )
+     * (reduce: type_declaration <- string_type_declaration)
+     *
+     *
+     * At first glance it seems that removing route 1 would make
+     * the most sense. Unfortunately the construct 'simple_spec_init'
+     * shows up multiple times in other rules, so changing this construct
+     * would also mean changing all the rules in which it appears.
+     * I (Mario) therefore chose to remove route 2 instead. This means
+     * that the above declaration gets stored in a
+     * simple_type_declaration_c, and not in a string_type_declaration_c
+     * as would be expected!
+     */
+    /*  string_type_name ':' elementary_string_type_name string_type_declaration_size string_type_declaration_init */
+#if 0
+SYM_REF4(string_type_declaration_c,	string_type_name,
+					elementary_string_type_name,
+					string_type_declaration_size,
+					string_type_declaration_init) /* may be == NULL! */
+#endif
+    void *visit(string_type_declaration_c *symbol);
+}; // type_initial_value_c
+
+
+