Synopsis

template <class SourcePosition>
struct get_prev_char;

This is a lazy template metafunction.

Description

Returns the last character the source position was updated with. The value it returns for start is unspecified.

Header

#include <boost/metaparse/get_prev_char.hpp>

Expression semantics

For any l, c compile-time wrapped integral values and ch compile-time wrapped character the following are equivalent

get_prev_char<source_position<l, c, ch>>::type

ch::type

Example

#include <boost/metaparse/get_prev_char.hpp>
#include <boost/metaparse/source_position.hpp>

#include <type_traits>

using namespace boost::metaparse;

struct returns_source_position
{
  using type =
    source_position<
      std::integral_constant<int, 11>,
      std::integral_constant<int, 13>,
      std::integral_constant<char, 'x'>
    >;
};

static_assert(
  get_prev_char<
    source_position<
      std::integral_constant<int, 11>,
      std::integral_constant<int, 13>,
      std::integral_constant<char, 'x'>
    >
  >::type::value == 'x',
  "It should return the prev. char of a source position"
);

static_assert(
  get_prev_char<returns_source_position>::type::value == 'x',
  "It should support lazy evaluation"
);