Strings vs expressions

[James Bonfield]

Hello all,

When is a expression within a string a real expression, and when is it just
part of the string?

Clearly not all $ symbols in strings form expressions. Eg dbiblast.acd
contains a string:

	pattern: "^([0-9]+.[0-9]+.[0-9]+)?$" 

Mostly complex expressions are wrapped in @(), but not always. Eg see
transeq.acd:

	def: $(sequence.begin)-$(sequence.end)

How can I tell expressions from just internal dollars. There doesn't appear to 
be any escaping syntax, which means this _must_ be clearly defined to avoid
bugs. My current ruling is if isn't followed by ( then it's not an
expression. Is that valid?

James

-- 
James Bonfield (jkb at mrc-lmb.cam.ac.uk)   Tel: 01223 402499   Fax: 01223 213556
Medical Research Council - Laboratory of Molecular Biology,
Hills Road, Cambridge, CB2 2QH, England.
Also see Staden Package WWW site at http://www.mrc-lmb.cam.ac.uk/pubseq/