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

   1 [#int_]
   2 [section int_]
   3
   4 [h1 Synopsis]
   5
   6   struct int_;
   7
   8 This is a [link parser parser].
   9
  10 [h1 Description]
  11
  12 It accepts a non-empty sequence of characters in the range `0-9`. The result of
  13 the parser is the decimal value represented by the accepted character sequence.
  14
  15 [h1 Header]
  16
  17   #include <boost/metaparse/int_.hpp>
  18
  19 [h1 Expression semantics]
  20
  21 The following are equivalent:
  22
  23   int_
  24
  25   foldl1<
  26     digit_val,
  27     boost::mpl::int_<0>,
  28     boost::mpl::lambda<
  29       boost::mpl::plus<
  30         boost::mpl::times<boost::mpl::_2, boost::mpl::int_<10>>,
  31         boost::mpl::_1
  32       >
  33     >::type
  34   >
  35
  36 [h1 Example]
  37
  38   #include <boost/metaparse/int_.hpp>
  39   #include <boost/metaparse/string.hpp>
  40   #include <boost/metaparse/start.hpp>
  41   #include <boost/metaparse/is_error.hpp>
  42   #include <boost/metaparse/get_result.hpp>
  43
  44   using namespace boost::metaparse;
  45
  46   static_assert(
  47     get_result<
  48       int_::apply<BOOST_METAPARSE_STRING("13"), start>
  49     >::type::value == 13,
  50     "It should parse an integer value"
  51   );
  52
  53   static_assert(
  54     is_error<int_::apply<BOOST_METAPARSE_STRING("six"), start>>::type::value,
  55     "It should reject the input if it is not a number"
  56   );
  57
  58 [endsect]
  59