73ef4ff3
 Hu Chunming
提交三方库
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[#letter]
[section letter]
[h1 Synopsis]
struct letter;
This is a [link parser parser].
[h1 Description]
Parser accepting one character in the range `a-z` or `A-Z`. The result of the
parser is the accepted character.
[h1 Header]
#include <boost/metaparse/letter.hpp>
[h1 Expression semantics]
The following are equivalent:
letter
accept_when<one_char, util::is_letter<>, error::letter_expected>
[h1 Example]
#include <boost/metaparse/letter.hpp>
#include <boost/metaparse/start.hpp>
#include <boost/metaparse/string.hpp>
#include <boost/metaparse/is_error.hpp>
#include <boost/metaparse/get_result.hpp>
using namespace boost::metaparse;
static_assert(
!is_error<letter::apply<BOOST_METAPARSE_STRING("a"), start>>::type::value,
"letter should accept a letter"
);
static_assert(
is_error<letter::apply<BOOST_METAPARSE_STRING("0"), start>>::type::value,
"letter should reject a digit"
);
static_assert(
get_result<
letter::apply<BOOST_METAPARSE_STRING("z"), start>
>::type::value == 'z',
"the result of parsing should be the character value"
);
[endsect]
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