digit.qbk
1.1 KB
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[#digit]
[section digit]
[h1 Synopsis]
struct digit;
This is a [link parser parser].
[h1 Description]
Parser accepting one character in the range `0-9`. The
result of the parser is the accepted character.
[h1 Header]
#include <boost/metaparse/digit.hpp>
[h1 Expression semantics]
The following are equivalent:
digit
accept_when<one_char, util::is_digit, error::digit_expected>
[h1 Example]
#include <boost/metaparse/digit.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<digit::apply<BOOST_METAPARSE_STRING("0"), start>>::type::value,
"digit should accept a digit"
);
static_assert(
is_error<digit::apply<BOOST_METAPARSE_STRING("x"), start>>::type::value,
"digit should reject a character"
);
static_assert(
get_result<
digit::apply<BOOST_METAPARSE_STRING("0"), start>
>::type::value == '0',
"the result of parsing should be the character value"
);
[endsect]