RE: [xml-dev] Ways of breaking out of normal interpretation and meaning

Thanks John. Good suggestion. I made the change:

http://www.xfront.com/Ways-of-Breaking-out-of-Normal-Interpretation-and-Meaning.pdf

/Roger


-----Original Message-----
From: John Cowan [mailto:] On Behalf Of John Cowan
Sent: Sunday, December 04, 2011 12:34 PM
To: Costello, Roger L.
Cc: 
Subject: Re: [xml-dev] Ways of breaking out of normal interpretation and meaning

Costello, Roger L. scripsit:

> In the regular expression language, the dash symbol is a special
> character that means range.  This regular expression says any digit
> from zero to nine:
> 
>     [0-9] 
> 
> By preceding the dash with a backslash:
> 
>     [0\-9]
> 
> we have broken the dash out of its normal meaning and it just becomes
> a meaningless character. The regex now says zero, dash, or nine.

This does work in XML Schema regular expressions, but I don't consider it
a good example, because many other implementations of regular expressions
do not support \-escaping inside character classes.  The conventional way
to write a character class meaning "zero, dash, or nine" is either
"[09-]" or "[-09].

A better example would be "a*", which means "zero or more 'a' characters",
whereas "a\*" means "an 'a' character followed by an '*' character".

-- 
John Cowan                                   
        "You need a change: try Canada"  "You need a change: try China"
                --fortune cookies opened by a couple that I know