ceph/src/boost/libs/metaparse/doc/foldl_reject_incomplete1.qbk

   1 [#foldl_reject_incomplete1]
   2 [section foldl_reject_incomplete1]
   3
   4 [h1 Synopsis]
   5
   6   template <class P, class State, class ForwardOp>
   7   struct foldl_reject_incomplete1;
   8
   9 This is a [link parser_combinator parser combinator].
  10
  11 [table Arguments
  12   [[Name]        [Type]]
  13   [[`P`]         [[link parser parser]]]
  14   [[`State`]     [[link metaprogramming_value template metaprogramming value]]]
  15   [[`ForwardOp`] [[link metafunction_class template metafunction class] taking two arguments]]
  16 ]
  17
  18 [h1 Description]
  19
  20 The same as [link foldl1 `foldl1`], but once `P` rejects the input,
  21 `foldl_reject_incomplete1` checks if `P` consumes any characters before
  22 rejecting the input. If so, `foldl_reject_incomplete1` rejects the input with
  23 the same error message this last application of `P` returned. Otherwise
  24 `foldl_reject_incomplete1` accepts the input and gives the same result as
  25 [link foldl1 `foldl1`].
  26
  27 [h1 Header]
  28
  29   #include <boost/metaparse/foldl_reject_incomplete1.hpp>
  30
  31 [h1 Expression semantics]
  32
  33 For any `p` parser, `t` class, `f` metafunction class taking two arguments,
  34 `s` compile-time string and `pos` source position
  35
  36   foldl_reject_incomplete1<p, t, f>::apply<s, pos>
  37
  38 is equivalent to
  39
  40   first_of<foldl1<p, t, f>, fail_at_first_char_expected<p> >::apply<s, pos>
  41
  42 [h1 Example]
  43
  44   #include <boost/metaparse/foldl_reject_incomplete1.hpp>
  45   #include <boost/metaparse/lit_c.hpp>
  46   #include <boost/metaparse/last_of.hpp>
  47   #include <boost/metaparse/token.hpp>
  48   #include <boost/metaparse/int_.hpp>
  49   #include <boost/metaparse/string.hpp>
  50   #include <boost/metaparse/start.hpp>
  51   #include <boost/metaparse/get_result.hpp>
  52   #include <boost/metaparse/is_error.hpp>
  53
  54   #include <boost/mpl/lambda.hpp>
  55   #include <boost/mpl/plus.hpp>
  56   #include <boost/mpl/int.hpp>
  57
  58   using namespace boost::metaparse;
  59
  60   using int_token = token<int_>;
  61   using plus_token = token<lit_c<'+'>>;
  62   using plus_int = last_of<plus_token, int_token>;
  63   using sum_op =
  64     boost::mpl::lambda<boost::mpl::plus<boost::mpl::_1, boost::mpl::_2>>::type;
  65
  66   using ints = foldl_reject_incomplete1<plus_int, boost::mpl::int_<11>, sum_op>;
  67
  68   static_assert(
  69     get_result<
  70       ints::apply<BOOST_METAPARSE_STRING("+ 13 + 3 + 21"), start>
  71     >::type::value == 48,
  72     "ints should sum the numbers"
  73   );
  74
  75   static_assert(
  76     is_error<
  77       ints::apply<BOOST_METAPARSE_STRING("+ 13 + 3 +"), start>
  78     >::type::value,
  79     "when the last number is missing, it should be an error"
  80   );
  81
  82   static_assert(
  83     is_error<ints::apply<BOOST_METAPARSE_STRING(""), start>>::type::value,
  84     "when no numbers are provided, it should be an error"
  85   );
  86
  87 [endsect]
  88