PatternMatch(39.0)	  ARP Programmers Manual    PatternMatch(39.0)



     ADDENDUM FOR
	  PatternMatch - perform a wildcard match on a string

     FUNCTION
	  The PatternMatch() wildcard characters have been changed in
	  the V39.0 (V1.3 of ARP) release.  Two of the unimplemented
	  wildcard characters specified in the earlier ARP releases
	  have been removed, and one new wildcard character has been
	  implemented.

	  Gone are the {} bracket characters, which were previously
	  reserved for use as tags for a replace function.  These
	  characters had been translated to wildcard tokens in prior
	  releases, which caused problems with some commercial software
	  packages that used the bracket characters (notably Word
	  Perfect).  The new implementation resolves this collision.

	  Also gone is the character class NOT construct, which was
	  specified by the characters [^].  Character classes are now
	  properly implemented using [] bracket characters, but the NOT
	  character class construct is gone.

	  Instead of the NOT character class, there is a generalized
	  NOT operator, specified with the TILDE character ~.  When
	  the NOT operator is specified, any pattern following the
	  NOT character must NOT be matched in order to return "true".
	  This is most useful for specifying something like "All files
	  that do NOT end in .info", which can be represented by:

	  	~*.info

	  A caution in the current implementation of NOT, users should
	  be aware that any TILDE character is translated to a NOT
	  token, and thus attempting to specify a literal TILDE
	  character must be escaped.  This is a particular issue for
	  users of MicroEmacs, which creates files that end in a tilde
	  character.  For instance, if you use the command:
	  
	  	>1 Delete *~

	  That will delete ALL files, rather than deleting all files
	  that end with the TILDE character.  That is because the NOT
	  operator requires a non-match on any following pattern.  In
	  order to actually delete all files ending in TILDE, you must
	  use:

		1> Delete *'~

	  This command uses the wildcard pattern ESCAPE character (the
	  single quote) to force the TILDE to be interpreted literally.
	  
	  A future implementation of the wildcard specs is likely to
	  have two changes from the V39 arp.library implementation.


     Page 1					    (printed 10/16/89)






     PatternMatch(39.0)	  ARP Programmers Manual    PatternMatch(39.0)



	  The first change will be to limit the scope of the NOT
	  operator, such that it will have the same scope as the #
	  "Match zero or more instances of the following substring"
	  operator.  Thus, the NOT operator would match "Exactly zero
	  instances of the following substring".  Substrings are
	  grouped as either the following character, or the following
	  wildcard token (such as a character class, or an OR clause).

	  The second change will be to interpret a trailing TILDE
	  character literally, since there is no following pattern to
	  match.  This is intended to resolve the collision with the
	  TILDE character in MicroEmacs.

	  These possible enhancements have been mentioned here to
	  assist applications developers who may want to use the NOT
	  operator within their applications programs.  In particular,
	  it would be advisable to use:

		~(*.info)

	  instead of:
	  
	  	~*.info

	  if you want to use the NOT operator for wildcard patterns.