tobiah wrote:
> Also, how does the engine decide whether I am adjusting
> the greed of the previous operator, or just asking
> for another possible character?
"?" always modifies the *preceeding* RE element.
if the preceeding element is a pattern (e.g. a character or group), it
means that the pattern is optional.
if the preceeding element is a repeat modifier (*, +, or ?), it changes
the greediness.
> Suppose I want:
>
> "x*?" to match "xxxxxxxO"
>
> If the '?' means non greedy, then I should get 'x' back.
no, because "*" means *ZERO* or more matches, not one or more.
> If the '?' means optional character then I should get
> the full string back.
no, because "?" never means anything on its own; it's a pattern
modifier, not a pattern.
> Checking in python:
>
> ######################################
> import re
>
> s = 'xxxxxxx0'
>
> m = re.search("x*", s)
> print "First way", m.group(0)
>
> m = re.search("x*?", s)
> print "Second way", m.group(0)
> #####################################
> First way xxxxxxx
> Second way
>
> So now I'm really confused. It didn't do a non-greedy
> 'x' match, nor did it allow the '?' to match the '0'.
see above. reading the RE documentation again may also help.
</F>
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