ceph/src/boost/libs/metaparse/doc/reject.qbk

   1 [#reject]
   2 [section reject]
   3
   4 [h1 Synopsis]
   5
   6   template <class Msg, class Pos>
   7   struct reject;
   8
   9 This is a [link metaprogramming_value template metaprogramming value].
  10
  11 [table Arguments
  12   [[Name]  [Type]]
  13   [[`Msg`] [[link metaprogramming_value template metaprogramming value]]]
  14   [[`Pos`] [[link source_position source position]]]
  15 ]
  16
  17 [h1 Description]
  18
  19 Values representing a failed parser application. It behaves as a
  20 [link lazy_metafunction lazy template metafunction]: when it is evaluated as a
  21 metafunction, it returns itself with its arguments evaluated. See expression
  22 semantics for further details.
  23
  24 [note
  25 Note that for backward compatibility when `Msg::type` is not defined,
  26 `reject<....>::type` does not evaluate `Msg`. For example
  27 `reject<int, start>::type` is `reject<int, start::type>`. Using types that are
  28 not template metaprogramming values as `Msg` is deprecated and will not work
  29 in future versions of the library.
  30 ]
  31
  32 [h1 Expressions semantics]
  33
  34 For any `m` template metaprogramming value and `p` source position the following
  35 are equivalent:
  36
  37   reject<m, p>::type
  38
  39   reject<m, p::type>
  40
  41 [h1 Header]
  42
  43   #include <boost/metaparse/reject.hpp>
  44
  45 [h1 Operations]
  46
  47 * [link get_position `get_position`]
  48 * [link get_message `get_message`]
  49
  50 [endsect]
  51