From: Jim Weirich <jim@...>
Date: 2005-08-25T09:31:55+09:00
Subject: Re: regexp character classes and +


Mark Volkmann said:
> Why is this a valid regular expression (+ not the first character in
> the character class)
>
> %r{^[-+*/]$}
>
> but this isn't? (+ is the first character in the character class)
>
> %r{^[+-*/]$}

Its not the '+' that is getting you ... its the '-'.

Inside brackets, the '-' means a range (e.g. 'A-Z' for the characters A
through Z).  But the range "+" (43) through "*" (42) is bad.

Inside brackets, the '-' loses its special meaning when it is the first
(or last) character.

-- 
-- Jim Weirich     jim@weirichhouse.org    http://onestepback.org
-----------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct,
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)