Synopsis

struct digit;

This is a parser.

Description

Parser accepting one character in the range 0-9. The result of the parser is the accepted character.

Header

#include <boost/metaparse/digit.hpp>

Expression semantics

The following are equivalent:

digit

accept_when<one_char, util::is_digit, error::digit_expected>

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"
);