projects / ceph.git / blame
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|---|---|---|
| 7c673cae FG |
1 | .. Algorithms/Concepts//Inserter |
| 2 | ||
| 3 | Inserter | |
| 4 | ======== | |
| 5 | ||
| 6 | Description | |
| 7 | ----------- | |
| 8 | ||
| 9 | An |Inserter| is a compile-time substitute for STL |Output Iterator|. | |
| 10 | Under the hood, it's simply a type holding | |
| 11 | two entities: a *state* and an *operation*. When passed to a | |
| 12 | |transformation algorithm|, the inserter's binary operation is | |
| 13 | invoked for every element that would normally be written into the | |
| 14 | output iterator, with the element itself (as the second | |
| 15 | argument) and the result of the previous operation's invocation |--| or, | |
| 16 | for the very first element, the inserter's initial state. | |
| 17 | ||
| 18 | Technically, instead of taking a single inserter parameter, | |
| 19 | |transformation algorithms| could accept the state and the "output" | |
| 20 | operation separately. Grouping these in a single parameter entity, | |
| 21 | however, brings the algorithms semantically and syntactically closer to | |
| 22 | their STL counterparts, significantly simplifying many of the common | |
| 23 | use cases. | |
| 24 | ||
| 25 | ||
| 26 | Valid expressions | |
| 27 | ----------------- | |
| 28 | ||
| 29 | |In the following table...| ``in`` is a model of |Inserter|. | |
| 30 | ||
| 31 | +-----------------------+-------------------------------+ | |
| 32 | | Expression | Type | | |
| 33 | +=======================+===============================+ | |
| 34 | | ``in::state`` | Any type | | |
| 35 | +-----------------------+-------------------------------+ | |
| 36 | | ``in::operation`` | Binary |Lambda Expression| | | |
| 37 | +-----------------------+-------------------------------+ | |
| 38 | ||
| 39 | ||
| 40 | Expression semantics | |
| 41 | -------------------- | |
| 42 | ||
| 43 | +-----------------------+-------------------------------------------+ | |
| 44 | | Expression | Semantics | | |
| 45 | +=======================+===========================================+ | |
| 46 | | ``in::state`` | The inserter's initial state. | | |
| 47 | +-----------------------+-------------------------------------------+ | |
| 48 | | ``in::operation`` | The inserter's "output" operation. | | |
| 49 | +-----------------------+-------------------------------------------+ | |
| 50 | ||
| 51 | ||
| 52 | Example | |
| 53 | ------- | |
| 54 | ||
| 55 | .. parsed-literal:: | |
| 56 | ||
| 57 | typedef transform< | |
| 58 | range_c<int,0,10> | |
| 59 | , plus<_1,_1> | |
| 60 | , back_inserter< vector0<> > | |
| 61 | >::type result; | |
| 62 | ||
| 63 | ||
| 64 | Models | |
| 65 | ------ | |
| 66 | ||
| 67 | * |[inserter]| | |
| 68 | * |front_inserter| | |
| 69 | * |back_inserter| | |
| 70 | ||
| 71 | See also | |
| 72 | -------- | |
| 73 | ||
| 74 | |Algorithms|, |Transformation Algorithms|, |[inserter]|, |front_inserter|, |back_inserter| | |
| 75 | ||
| 76 | ||
| 77 |