[#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]