AW: How trim: Bug in RegExp engine

[Ken Ray]

On 10/24/05 4:51 PM, "Marielle Lange" <mlange at lexicall.org> wrote:

> Yuk!!!
> 
> If the programmers have to check up regular expressions anyway, can I
> suggest they make the matchtext consider the full text and not just
> match ***within*** a line of text. Okay for "^" and "$" to correspond
> to the start and end of a line of text, this is what happens in all
> programs that allow for regular expression.
> 
> But in all programs that implement regular expressions, the following
> happens:
> put replaceText("DA" & cr & "CD","A.?C","")    -> DD
> put replaceText("DA" & tab & "CD","A.?C","") -> DD
> 
> In revolution, this happens:
> put replaceText("DA" & cr & "CD","A.?C","")    -> DA cr CD
> put replaceText("DA" & tab & "CD","A.?C","") -> DD

This is because the PCRE engine needs to be explicitly told that you want to
treat multiple lines as a single "block", otherwise it looks for a match on
each line. To do this, you need to preface the expression with "(?s)", as
in:

  put replaceText("DA" & cr & "CD","(?s)A.?C","")

and you get back "DD" as you'd expect. (For more info, see the docs at
http://www.pcre.org/man.txt.)

Ken Ray
Sons of Thunder Software
Web site: http://www.sonsothunder.com/
Email: kray at sonsothunder.com