Synopsis

struct letter;

This is a parser.

Description

Parser accepting one character in the range a-z or A-Z. The result of the parser is the accepted character.

Header

#include <boost/metaparse/letter.hpp>

Expression semantics

The following are equivalent:

letter

accept_when<one_char, util::is_letter<>, error::letter_expected>

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"
);