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| 2 | [section:archetypes Iterator Archetypes] | |
| 3 | ||
| 4 | The `iterator_archetype` class constructs a minimal implementation of | |
| 5 | one of the iterator access concepts and one of the iterator traversal concepts. | |
| 6 | This is used for doing a compile-time check to see if a the type requirements | |
| 7 | of a template are really enough to cover the implementation of the template. | |
| 8 | For further information see the documentation for the |concepts|_ library. | |
| 9 | ||
| 10 | [h2 Synopsis] | |
| 11 | ||
| 12 | namespace iterator_archetypes | |
| 13 | { | |
| 14 | // Access categories | |
| 15 | ||
| 16 | typedef /*implementation defined*/ readable_iterator_t; | |
| 17 | typedef /*implementation defined*/ writable_iterator_t; | |
| 18 | typedef /*implementation defined*/ readable_writable_iterator_t; | |
| 19 | typedef /*implementation defined*/ readable_lvalue_iterator_t; | |
| 20 | typedef /*implementation defined*/ writable_lvalue_iterator_t; | |
| 21 | ||
| 22 | } | |
| 23 | ||
| 24 | template < | |
| 25 | class Value | |
| 26 | , class AccessCategory | |
| 27 | , class TraversalCategory | |
| 28 | > | |
| 29 | class iterator_archetype | |
| 30 | { | |
| 31 | typedef /* see below */ value_type; | |
| 32 | typedef /* see below */ reference; | |
| 33 | typedef /* see below */ pointer; | |
| 34 | typedef /* see below */ difference_type; | |
| 35 | typedef /* see below */ iterator_category; | |
| 36 | }; | |
| 37 | ||
| 38 | [h3 Access Category Tags] | |
| 39 | ||
| 40 | The access category types provided correspond to the following | |
| 41 | standard iterator access concept combinations: | |
| 42 | ||
| 43 | readable_iterator_t := | |
| 44 | ||
| 45 | Readable Iterator | |
| 46 | ||
| 47 | writable_iterator_t := | |
| 48 | ||
| 49 | Writeable Iterator | |
| 50 | ||
| 51 | readable_writable_iterator_t := | |
| 52 | ||
| 53 | Readable Iterator & Writeable Iterator & Swappable Iterator | |
| 54 | ||
| 55 | readable_lvalue_iterator_t := | |
| 56 | ||
| 57 | Readable Iterator & Lvalue Iterator | |
| 58 | ||
| 59 | writeable_lvalue_iterator_t := | |
| 60 | ||
| 61 | Readable Iterator & Writeable Iterator & Swappable Iterator & Lvalue Iterator | |
| 62 | ||
| 63 | [h3 Traits] | |
| 64 | ||
| 65 | The nested trait types are defined as follows: | |
| 66 | ||
| 67 | ||
| 68 | if (AccessCategory == readable_iterator_t) | |
| 69 | ||
| 70 | value_type = Value | |
| 71 | reference = Value | |
| 72 | pointer = Value* | |
| 73 | ||
| 74 | else if (AccessCategory == writable_iterator_t) | |
| 75 | ||
| 76 | value_type = void | |
| 77 | reference = void | |
| 78 | pointer = void | |
| 79 | ||
| 80 | else if (AccessCategory == readable_writable_iterator_t) | |
| 81 | ||
| 82 | value_type = Value | |
| 83 | ||
| 84 | reference := | |
| 85 | ||
| 86 | A type X that is convertible to Value for which the following | |
| 87 | expression is valid. Given an object x of type X and v of type | |
| 88 | Value. | |
| 89 | ||
| 90 | x = v | |
| 91 | ||
| 92 | pointer = Value* | |
| 93 | ||
| 94 | else if (AccessCategory == readable_lvalue_iterator_t) | |
| 95 | ||
| 96 | value_type = Value | |
| 97 | reference = Value const& | |
| 98 | pointer = Value const* | |
| 99 | ||
| 100 | else if (AccessCategory == writable_lvalue_iterator_t) | |
| 101 | ||
| 102 | value_type = Value | |
| 103 | reference = Value& | |
| 104 | pointer = Value* | |
| 105 | ||
| 106 | if ( TraversalCategory is convertible to forward_traversal_tag ) | |
| 107 | ||
| 108 | difference_type := ptrdiff_t | |
| 109 | ||
| 110 | else | |
| 111 | ||
| 112 | difference_type := unspecified type | |
| 113 | ||
| 114 | ||
| 115 | iterator_category := | |
| 116 | ||
| 117 | A type X satisfying the following two constraints: | |
| 118 | ||
| 119 | 1. X is convertible to X1, and not to any more-derived | |
| 120 | type, where X1 is defined by: | |
| 121 | ||
| 122 | if (reference is a reference type | |
| 123 | && TraversalCategory is convertible to forward_traversal_tag) | |
| 124 | { | |
| 125 | if (TraversalCategory is convertible to random_access_traversal_tag) | |
| 126 | X1 = random_access_iterator_tag | |
| 127 | else if (TraversalCategory is convertible to bidirectional_traversal_tag) | |
| 128 | X1 = bidirectional_iterator_tag | |
| 129 | else | |
| 130 | X1 = forward_iterator_tag | |
| 131 | } | |
| 132 | else | |
| 133 | { | |
| 134 | if (TraversalCategory is convertible to single_pass_traversal_tag | |
| 135 | && reference != void) | |
| 136 | X1 = input_iterator_tag | |
| 137 | else | |
| 138 | X1 = output_iterator_tag | |
| 139 | } | |
| 140 | ||
| 141 | 2. X is convertible to TraversalCategory | |
| 142 | ||
| 143 | ||
| 144 | [h2 Requirements] | |
| 145 | ||
| 146 | The `AccessCategory` argument must be one of the predefined access | |
| 147 | category tags. The `TraversalCategory` must be one of the standard | |
| 148 | traversal tags. The `Value` type must satisfy the requirements of | |
| 149 | the iterator concept specified by `AccessCategory` and | |
| 150 | `TraversalCategory` as implied by the nested traits types. | |
| 151 | ||
| 152 | [h2 Concepts] | |
| 153 | ||
| 154 | `iterator_archetype` models the iterator concepts specified by the | |
| 155 | `AccessCategory` and `TraversalCategory` | |
| 156 | arguments. `iterator_archetype` does not model any other access | |
| 157 | concepts or any more derived traversal concepts. | |
| 158 | ||
| 159 | ||
| 160 | [endsect] |