AW: How trim: Bug in RegExp engine

[Thomas Fischer]

Hi,

Wouter is right:

> It is indeed elegant, but a condition check is necessary here as it  
> will remove the first word + the space(s) if there is no space at the  
> start of the line.
> 
> > "        The cat sat on the mat.         "

> But if no space in front the result is
> 
> "cat sat on the mat.         "
> 

This is actually true -- and a serious bug in Revolution's RegExp engine.

The Regular Expression Syntax reference states:

^ matches the following character at the beginning of the string
^A matches "ABC" but not "CAB"

* matches zero or more occurrences of the preceding character or pattern

I assumed that Revolution would do what it promised and didn't check this.

Try
answer replaceText("A C","^ *","")
I get "C", which obviously is not correct.
If I remove the "*", I get "A C"

And
answer replaceText("BAC","^A*","")
gives "C", so "^A*" matches "BA".
This must not happen.

It looks like "^A*" is incorrectly interpreted as "^.*A*".

Parentheses don't help, but might make things worse:
answer replaceText("BAC","(^A)*","")
gives an empty result. No idea why.

All the best
Thomas


--
Thomas Fischer
Salzburg