29 * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10) |
29 * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10) |
30 * |
30 * |
31 */ |
31 */ |
32 |
32 |
33 |
33 |
34 /* Determine the data type on which another data type is based on. |
34 /* Determine the data type on which another data type is based on. */ |
35 * If a new default initial value is given, we DO NOT consider it a |
35 |
36 * new base class, and continue looking further! |
36 /* |
37 * |
37 * What is a Base Type? |
38 * E.g. TYPE new_int_t : INT; END_TYPE; |
38 * A base type is the fundamental data type from which the type is derived. |
39 * TYPE new_int2_t : INT = 2; END_TYPE; |
39 * The main idea is that if two datatyes (A and B) share a common base type, |
40 * TYPE new_subr_t : INT (4..5); END_TYPE; |
40 * then these two datatypes may be used interchangeably in an expression. |
41 * |
41 * |
42 * new_int_t is really an INT!! |
42 * What is an Equivalent Type? |
43 * new_int2_t is also really an INT!! |
43 * An equivalent type is the data type from which the type is derived. |
44 * new_subr_t is also really an INT!! |
44 * The Base type and the Equivalent type will always be the same, with the |
45 * |
45 * exception of subranges! |
46 * Note that a FB declaration is also considered a base type, as |
46 * |
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47 * E.g. TYPE new_int_t : INT; END_TYPE; |
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48 * TYPE new_int2_t : INT := 2; END_TYPE; |
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49 * TYPE new_int3_t : new_int2_t := 3; END_TYPE; |
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50 * TYPE new_sub_t : INT (4..10); END_TYPE; |
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51 * TYPE new_sub2_t : new_sub_t := 5 ; END_TYPE; |
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52 * TYPE new_sub3_t : new_sub2_t := 6 ; END_TYPE; |
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53 * TYPE new_sub4_t : new_int3_t (4..10); END_TYPE; <----- This is NOT legal syntax! |
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54 * |
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55 * new_int_t : base type->INT equivalent type->INT |
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56 * new_int2_t : base type->INT equivalent type->INT |
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57 * new_int3_t : base type->INT equivalent type->INT |
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58 * new_sub_t : base type->INT equivalent type->new_sub_t |
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59 * new_sub2_t : base type->INT equivalent type->new_sub_t |
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60 * new_sub3_t : base type->INT equivalent type->new_sub_t |
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61 * |
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62 * Note too that a FB declaration is also considered a base type, as |
47 * we may have FB instances declared of a specific FB type. |
63 * we may have FB instances declared of a specific FB type. |
48 */ |
64 */ |
49 |
65 |
50 |
66 |
51 class search_base_type_c: public null_visitor_c { |
67 class search_base_type_c: public null_visitor_c { |
52 |
68 |
53 private: |
69 private: |
54 symbol_c *current_type_name; |
70 symbol_c *current_basetype_name; |
55 symbol_c *current_basetype; |
71 symbol_c *current_basetype; |
56 bool is_array; |
72 symbol_c *current_equivtype; |
57 bool is_subrange; |
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58 bool is_enumerated; |
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59 bool is_fb; |
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60 static search_base_type_c *search_base_type_singleton; // Make this a singleton class! |
73 static search_base_type_c *search_base_type_singleton; // Make this a singleton class! |
61 |
74 |
62 private: |
75 private: |
63 static void create_singleton(void); |
76 static void create_singleton(void); |
64 |
77 |
65 public: |
78 public: |
66 search_base_type_c(void); |
79 search_base_type_c(void); |
67 static symbol_c *get_basetype_decl (symbol_c *symbol); |
80 static symbol_c *get_equivtype_decl(symbol_c *symbol); /* get the Equivalent Type declaration */ |
68 static symbol_c *get_basetype_id (symbol_c *symbol); |
81 static symbol_c *get_basetype_decl (symbol_c *symbol); /* get the Base Type declaration */ |
69 static bool type_is_subrange (symbol_c *type_decl); |
82 static symbol_c *get_basetype_id (symbol_c *symbol); /* get the Base Type identifier */ |
70 static bool type_is_enumerated(symbol_c *type_decl); |
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71 static bool type_is_fb (symbol_c *type_decl); |
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72 |
83 |
73 public: |
84 public: |
74 /*************************/ |
85 /*************************/ |
75 /* B.1 - Common elements */ |
86 /* B.1 - Common elements */ |
76 /*************************/ |
87 /*************************/ |