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

   1 [#sequence_apply]
   2 [section sequence_apply]
   3
   4 [h1 Synopsis]
   5
   6   template <template <class, ..., class> class T, class P1, ..., class Pn>
   7   struct sequence_applyn;
   8
   9 This is a [link parser_combinator parser combinator].
  10
  11 [table Arguments
  12   [[T] [Template class taking `n` arguments]]
  13   [[`P1`..`Pn`]  [[link parser parser]s]]
  14 ]
  15
  16 [h1 Description]
  17
  18 It applies the `P1` ... `Pn` [link parser parser]s on the input in order. When
  19 all of them succeed, the result of parsing with `sequence_applyn` is the `T`
  20 template class instantiated with the results of the `P1` ... `Pn`
  21 [link parser parser]s. When any of the `P1` ... `Pn` [link parser parser]s
  22 reject the input, the error is propagated.
  23
  24 `n` has to be in the `[1..BOOST_METAPARSE_LIMIT_SEQUENCE_SIZE)` range.
  25
  26 [h1 Header]
  27
  28   #include <boost/metaparse/sequence_apply.hpp>
  29
  30 [h1 Expression semantics]
  31
  32 For any `n > 0`, `p1` ... `pn` [link parser parser]s, `t` template class with
  33 `n` `class` arguments, `s` compile-time string and `pos` source position the
  34 following are equivalent:
  35
  36   sequence_apply<t, p1, ..., pn>::apply<s, pos>::type
  37
  38 when [link sequence `sequence`]`<p1, ..., pn>` accepts the input:
  39
  40   return_<
  41     t<
  42       mpl::at_c<0, get_result<sequence<p1,...,pn>::apply<s, pos>>::type>::type,
  43       ...
  44       mpl::at_c<n, get_result<sequence<p1,...,pn>::apply<s, pos>>::type>::type,
  45     >
  46   >::apply<s, pos>::type
  47
  48 when [link sequence `sequence`]`<p1, ..., pn>` rejects the input:
  49
  50   sequence<p1, ..., pn>::apply<s, pos>::type
  51
  52 [h1 Example]
  53
  54   #include <boost/metaparse/sequence_apply.hpp>
  55   #include <boost/metaparse/int_.hpp>
  56   #include <boost/metaparse/middle_of.hpp>
  57   #include <boost/metaparse/lit_c.hpp>
  58   #include <boost/metaparse/start.hpp>
  59   #include <boost/metaparse/string.hpp>
  60   #include <boost/metaparse/get_result.hpp>
  61
  62   #include <boost/type_traits/is_same.hpp>
  63
  64   using namespace boost::metaparse;
  65
  66   template <int Real, int Imaginary>
  67   struct complex_c { typedef complex_c type; };
  68
  69   template <class Real, class Imaginary>
  70   struct complex : complex_c<Real::type::value, Imaginary::type::value> {};
  71
  72   typedef
  73     sequence_apply2<complex, int_, middle_of<lit_c<'+'>, int_, lit_c<'i'>>>
  74     complex_parser;
  75
  76   static_assert(
  77     boost::is_same<
  78       complex_c<1, 2>,
  79       get_result<
  80         complex_parser::apply<BOOST_METAPARSE_STRING("1+2i"), start>
  81       >::type::type
  82     >::type::value,
  83     "the result of parsing should be the list of digit values"
  84   );
  85
  86 [endsect]
  87