TAP::Parser::Grammar(3pm)				 Perl Programmers Reference Guide				 TAP::Parser::Grammar(3pm)

NAME

       TAP::Parser::Grammar - A grammar for the Test Anything Protocol.

VERSION

       Version 3.17

SYNOPSIS

	 use TAP::Parser::Grammar;
	 my $grammar = $self->make_grammar({
	   stream  => $tap_parser_stream,
	   parser  => $tap_parser,
	   version => 12,
	 });

	 my $result = $grammar->tokenize;

DESCRIPTION

       "TAP::Parser::Grammar" tokenizes lines from a TAP stream and constructs TAP::Parser::Result subclasses to represent the tokens.

       Do not attempt to use this class directly.  It won't make sense.  It's mainly here to ensure that we will be able to have pluggable
       grammars when TAP is expanded at some future date (plus, this stuff was really cluttering the parser).

METHODS

   Class Methods
       "new"

	 my $grammar = TAP::Parser::Grammar->new({
	     stream  => $stream,
	     parser  => $parser,
	     version => $version,
	 });

       Returns TAP::Parser grammar object that will parse the specified stream.  Both "stream" and "parser" are required arguments.  If "version"
       is not set it defaults to 12 (see "set_version" for more details).

   Instance Methods
       "set_version"

	 $grammar->set_version(13);

       Tell the grammar which TAP syntax version to support. The lowest supported version is 12. Although 'TAP version' isn't valid version 12
       syntax it is accepted so that higher version numbers may be parsed.

       "tokenize"

	 my $token = $grammar->tokenize;

       This method will return a TAP::Parser::Result object representing the current line of TAP.

       "token_types"

	 my @types = $grammar->token_types;

       Returns the different types of tokens which this grammar can parse.

       "syntax_for"

	 my $syntax = $grammar->syntax_for($token_type);

       Returns a pre-compiled regular expression which will match a chunk of TAP corresponding to the token type.  For example (not that you
       should really pay attention to this, "$grammar->syntax_for('comment')" will return "qr/^#(.*)/".

       "handler_for"

	 my $handler = $grammar->handler_for($token_type);

       Returns a code reference which, when passed an appropriate line of TAP, returns the lexed token corresponding to that line.  As a result,
       the basic TAP parsing loop looks similar to the following:

	my @tokens;
	my $grammar = TAP::Grammar->new;
	LINE: while ( defined( my $line = $parser->_next_chunk_of_tap ) ) {
	    foreach my $type ( $grammar->token_types ) {
		my $syntax  = $grammar->syntax_for($type);
		if ( $line =~ $syntax ) {
		    my $handler = $grammar->handler_for($type);
		    push @tokens => $grammar->$handler($line);
		    next LINE;
		}
	    }
	    push @tokens => $grammar->_make_unknown_token($line);
	}

TAP GRAMMAR

       NOTE:  This grammar is slightly out of date.  There's still some discussion about it and a new one will be provided when we have things
       better defined.

       The TAP::Parser does not use a formal grammar because TAP is essentially a stream-based protocol.  In fact, it's quite legal to have an
       infinite stream.  For the same reason that we don't apply regexes to streams, we're not using a formal grammar here.  Instead, we parse the
       TAP in lines.

       For purposes for forward compatability, any result which does not match the following grammar is currently referred to as
       TAP::Parser::Result::Unknown.  It is not a parse error.

       A formal grammar would look similar to the following:

	(*
	    For the time being, I'm cheating on the EBNF by allowing
	    certain terms to be defined by POSIX character classes by
	    using the following syntax:

	      digit ::= [:digit:]

	    As far as I am aware, that's not valid EBNF.  Sue me.  I
	    didn't know how to write "char" otherwise (Unicode issues).
	    Suggestions welcome.
	*)

	tap	       ::= version? { comment | unknown } leading_plan lines
			   |
			   lines trailing_plan {comment}

	version        ::= 'TAP version ' positiveInteger {positiveInteger} "
"

	leading_plan   ::= plan skip_directive? "
"

	trailing_plan  ::= plan "
"

	plan	       ::= '1..' nonNegativeInteger

	lines	       ::= line {line}

	line	       ::= (comment | test | unknown | bailout ) "
"

	test	       ::= status positiveInteger? description? directive?

	status	       ::= 'not '? 'ok '

	description    ::= (character - (digit | '#')) {character - '#'}

	directive      ::= todo_directive | skip_directive

	todo_directive ::= hash_mark 'TODO' ' ' {character}

	skip_directive ::= hash_mark 'SKIP' ' ' {character}

	comment        ::= hash_mark {character}

	hash_mark      ::= '#' {' '}

	bailout        ::= 'Bail out!' {character}

	unknown        ::= { (character - "
") }

	(* POSIX character classes and other terminals *)

	digit		   ::= [:digit:]
	character	   ::= ([:print:] - "
")
	positiveInteger    ::= ( digit - '0' ) {digit}
	nonNegativeInteger ::= digit {digit}

SUBCLASSING

       Please see "SUBCLASSING" in TAP::Parser for a subclassing overview.

       If you really want to subclass TAP::Parser's grammar the best thing to do is read through the code.  There's no easy way of summarizing it
       here.

SEE ALSO

       TAP::Object, TAP::Parser, TAP::Parser::Iterator, TAP::Parser::Result,

perl v5.12.1							    2010-04-26						 TAP::Parser::Grammar(3pm)