118 lines
2.7 KiB
Plaintext
118 lines
2.7 KiB
Plaintext
[#next_char]
|
|
[section next_char]
|
|
|
|
[h1 Synopsis]
|
|
|
|
template <class SourcePosition, class Ch>
|
|
struct next_char;
|
|
|
|
This is a [link lazy_metafunction lazy template metafunction].
|
|
|
|
[table Arguments
|
|
[[Name] [Type]]
|
|
[[`SourcePosition`] [[link source_position source position]]]
|
|
[[`Ch`] [[link boxed_value boxed] character value. The character `SourcePosition` points to in the input.]]
|
|
]
|
|
|
|
[h1 Description]
|
|
|
|
Returns a new source position, pointing to the next character of the same line.
|
|
|
|
[h1 Header]
|
|
|
|
#include <boost/metaparse/next_char.hpp>
|
|
|
|
[h1 Expression semantics]
|
|
|
|
For any `s` source position and `c` wrapped character the following are
|
|
equivalent
|
|
|
|
get_col<next_char<s, c>>
|
|
|
|
boost::mpl::plus<get_col<s>::type, boost::mpl::int_<1>>
|
|
|
|
get_line<next_char<s, c>>
|
|
|
|
get_line<s>
|
|
|
|
get_prev_char<next_char<s, c>>::type
|
|
|
|
c
|
|
|
|
[h1 Example]
|
|
|
|
#include <boost/metaparse/next_char.hpp>
|
|
#include <boost/metaparse/source_position.hpp>
|
|
#include <boost/metaparse/get_col.hpp>
|
|
#include <boost/metaparse/get_line.hpp>
|
|
#include <boost/metaparse/get_prev_char.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, 'a'>
|
|
>;
|
|
};
|
|
|
|
struct returns_char
|
|
{
|
|
using type = std::integral_constant<char, 'x'>;
|
|
};
|
|
|
|
static_assert(
|
|
get_col<
|
|
next_char<
|
|
source_position<
|
|
std::integral_constant<int, 11>,
|
|
std::integral_constant<int, 13>,
|
|
std::integral_constant<char, 'a'>
|
|
>,
|
|
std::integral_constant<char, 'x'>
|
|
>
|
|
>::type::value == 14,
|
|
"it should increase the column component of the source position"
|
|
);
|
|
|
|
static_assert(
|
|
get_line<
|
|
next_char<
|
|
source_position<
|
|
std::integral_constant<int, 11>,
|
|
std::integral_constant<int, 13>,
|
|
std::integral_constant<char, 'a'>
|
|
>,
|
|
std::integral_constant<char, 'x'>
|
|
>
|
|
>::type::value == 11,
|
|
"it should not increase the line component of the source position"
|
|
);
|
|
|
|
static_assert(
|
|
get_prev_char<
|
|
next_char<
|
|
source_position<
|
|
std::integral_constant<int, 11>,
|
|
std::integral_constant<int, 13>,
|
|
std::integral_constant<char, 'a'>
|
|
>,
|
|
std::integral_constant<char, 'x'>
|
|
>
|
|
>::type::value == 'x',
|
|
"it should update the prev char component of the source position"
|
|
);
|
|
|
|
static_assert(
|
|
get_col<next_char<returns_source_position, returns_char>>::type::value == 14,
|
|
"it should support lazy evaluation"
|
|
);
|
|
|
|
[endsect]
|
|
|