Path: utzoo!attcan!uunet!mcvax!ukc!reading!cf-cm!ted
From: ted@computing-maths.cardiff.ac.uk (Ted Lawson)
Newsgroups: comp.lang.eiffel
Subject: Suggested modifications to syntax definition in OOSC
Keywords: Eiffel syntax
Message-ID: <830@cf-cm.UUCP>
Date: 22 Jul 89 13:37:58 GMT
Organization: University of Wales College of Cardiff, Cardiff, WALES, UK.
Lines: 57



   There are two parts of the Eiffel grammar published in OOSC that
   could be represented in ways that reflect their semantics better.
   Both concern expressions.

1) The production

	Expression		= 	{Unqualified_expression "." ...}

   allows tokens other than class features to follow a ".". For example
   the following nonsensical constructs will be recognised as Expressions

			"1.2.3"
			"x.Current.Current"
			"x.( 1 + 2 )"

			etc.

   I suggest this as an alternative:

	Expression		=	Unqualified_expression | 
					Expression "." Entity |
					Expression "." Unqualified_call

2) The syntax defining Multiary_expressions

	Expression		= 	{Unqualified_expression "." ...}
	Unqualified_expression	=	Constant | (omitted) |
					Operator_expression

	Multiary_expression	=	{Expression Multiary ... }+

   is (if I understand Bertrand Meyer's use of the {...} notation correctly)
   semantically rather curious. For example, it means that
	
			"123"

   is a Multiary_expression.

   An alternative:

	Multiary_expression	=	Expression Multiary
						{Expression Multiary ... }+

  or recursively:

	Multiary_expression	=	Expression Multiary Expression |
					Multiary_expression Multiary Expression


                      ================================

   Any comments on these remarks are very welcome.

   Ted Lawson
   ted@uk.ac.cf.cm