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

   1 [#int_to_digit]
   2 [section int_to_digit]
   3
   4 [h1 Synopsis]
   5
   6   namespace util
   7   {
   8     template <class D>
   9     struct int_to_digit;
  10   }
  11
  12 This is a [link lazy_metafunction lazy template metafunction] that supports
  13 [link currying currying].
  14
  15 [table Arguments
  16   [[Name] [Type]]
  17   [[`D`]  [[link boxed_value boxed] integer value]]
  18 ]
  19
  20 [h1 Description]
  21
  22 Converts a boxed integer value in the range `[0-9]` to a character representing
  23 that decimal value.
  24
  25 [h1 Header]
  26
  27   #include <boost/metaparse/util/int_to_digit.hpp>
  28
  29 [h1 Expression semantics]
  30
  31 The following pairs of expressions are equivalent
  32
  33   int_to_digit<boost::mpl::int_<0>>::type
  34   boost::mpl::char_<'0'>
  35
  36   int_to_digit<boost::mpl::int_<9>>::type
  37   boost::mpl::char_<'9'>
  38
  39 [h1 Example]
  40
  41   #include <boost/metaparse/util/int_to_digit.hpp>
  42
  43   #include <type_traits>
  44
  45   using namespace boost::metaparse;
  46
  47   struct nullary_metafunction_returning_4
  48   {
  49     using type = std::integral_constant<int, 4>;
  50   };
  51
  52   static_assert(
  53     util::int_to_digit<std::integral_constant<int, 0>>::type::value == '0',
  54     "it should convert an integer value to the corresponding character"
  55   );
  56
  57   static_assert(
  58     util::int_to_digit<>::type
  59       ::apply<std::integral_constant<int, 7>>::type::value == '7',
  60     "it should support currying"
  61   );
  62
  63   static_assert(
  64     util::int_to_digit<nullary_metafunction_returning_4>::type::value == '4',
  65     "it should support lazy evaluation"
  66   );
  67
  68 [endsect]
  69