I'm trying to develop a lexer for Oracle 9i PL/SQL.

I'm struggling with the lexical rule for PL/SQL
numbers. My grammar works for all examples except for
a real number that starts with a decimal point,
e.g. .123 . All my attempts to cater for this run into
ambiguity problems with the component selector
operator ('.') and the range operator ('..').

Can anyone tell me what I should 'tweak' in this
grammar thatI've adapted from the ADA one on the Antlr
site.

			

			************************************************
			

			NUMBER  :
			

			( DIGIT )+
			

			( { LA(2)!='.' && LA(3)!='.' }?
			

			( '.' ( DIGIT )* ( EXPONENT )?
			

			| EXPONENT
			

			)
			

			)?
			

			;
			

			

			protected
			

			EXPONENT           :  ('e') ('+'|'-')? ( DIGIT )+ ;
			

			

			// a couple protected methods to assist in matching the various numbers
			

			protected
			

			DIGIT   :  ( '0'..'9' ) ;
			

			

			// Operators
			

			COMPSEL       :   '.'  ;
			

			RANGE         :   ".." ;
			

			

			*******************************************
			

			From the PL/SQL User Guide and Reference:
			

			"Two kinds of numeric literals can be used in arithmetic
			

			expressions: integers and reals. An integer literal
			

			is an optionally signed whole number without a
			

			decimal point.
			

			

			

			Some examples follow:
			

			

			030 6 -14 0 +32767
			

			

			A real literal is an optionally signed whole or fractional
			

			number with a decimal point. Several examples follow:
			

			

			6.6667 0.0 -12.0 3.14159 +8300.00 .5 25.
			

			

			PL/SQL considers numbers such as 12.0 and 25. to be reals
			

			even though they have integral values."