projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | .. Metafunctions/Concepts//Metafunction Class |20 |
| 2 | ||
| 3 | Metafunction Class | |
| 4 | ================== | |
| 5 | ||
| 6 | Summary | |
| 7 | ------- | |
| 8 | ||
| 9 | A *metafunction class* is a certain form of metafunction representation | |
| 10 | that enables higher-order metaprogramming. More precisely, it's a class | |
| 11 | with a publicly-accessible nested |metafunction| called ``apply``. | |
| 12 | Correspondingly, a metafunction class invocation is defined as invocation | |
| 13 | of its nested ``apply`` metafunction. | |
| 14 | ||
| 15 | ||
| 16 | Expression requirements | |
| 17 | ----------------------- | |
| 18 | ||
| 19 | |In the following table...| ``f`` is a |Metafunction Class|. | |
| 20 | ||
| 21 | +-------------------------------+---------------------------+---------------------------+ | |
| 22 | | Expression | Type | Complexity | | |
| 23 | +===============================+===========================+===========================+ | |
| 24 | | ``f::apply::type`` | Any type | Unspecified. | | |
| 25 | +-------------------------------+---------------------------+---------------------------+ | |
| 26 | | ``f::apply<>::type`` | Any type | Unspecified. | | |
| 27 | +-------------------------------+---------------------------+---------------------------+ | |
| 28 | | ``f::apply<a1,...an>::type`` | Any type | Unspecified. | | |
| 29 | +-------------------------------+---------------------------+---------------------------+ | |
| 30 | ||
| 31 | ||
| 32 | Expression semantics | |
| 33 | -------------------- | |
| 34 | ||
| 35 | .. parsed-literal:: | |
| 36 | ||
| 37 | typedef f::apply::type x; | |
| 38 | ||
| 39 | :Precondition: | |
| 40 | ``f`` is a nullary |Metafunction Class|; ``f::apply::type`` is a *type-name*. | |
| 41 | ||
| 42 | :Semantics: | |
| 43 | ``x`` is the result of the metafunction class invocation. | |
| 44 | ||
| 45 | ||
| 46 | .. ................................................................................... | |
| 47 | ||
| 48 | .. parsed-literal:: | |
| 49 | ||
| 50 | typedef f::apply<>::type x; | |
| 51 | ||
| 52 | :Precondition: | |
| 53 | ``f`` is a nullary |Metafunction Class|; ``f::apply<>::type`` is a *type-name*. | |
| 54 | ||
| 55 | :Semantics: | |
| 56 | ``x`` is the result of the metafunction class invocation. | |
| 57 | ||
| 58 | ||
| 59 | .. ................................................................................... | |
| 60 | ||
| 61 | .. parsed-literal:: | |
| 62 | ||
| 63 | typedef f::apply<a1,\ |...|\ a\ *n*\>::type x; | |
| 64 | ||
| 65 | :Precondition: | |
| 66 | ``f`` is an *n*-ary metafunction class; ``apply`` is a |Metafunction|. | |
| 67 | ||
| 68 | :Semantics: | |
| 69 | ``x`` is the result of the metafunction class | |
| 70 | invocation with the actual arguments |a1...an|. | |
| 71 | ||
| 72 | ||
| 73 | Models | |
| 74 | ------ | |
| 75 | ||
| 76 | * |always| | |
| 77 | * |arg| | |
| 78 | * |quote| | |
| 79 | * |numeric_cast| | |
| 80 | * |unpack_args| | |
| 81 | ||
| 82 | ||
| 83 | See also | |
| 84 | -------- | |
| 85 | ||
| 86 | |Metafunctions|, |Metafunction|, |Lambda Expression|, |Invocation|, |apply_wrap|, |bind|, |quote| | |
| 87 | ||
| 88 | ||
| 89 |