Regular Expression: Matching substring

[Leon]

Hi Kevin,

You may notice that, for matching the regex (0|(1(01*0)*1))*,  the left
most
three  characters of a string must not be ``101" while not followed by
an `0'.
After reading the first `1', automata expects  `1' or ``00" or ``010"
or ``11",
right?:)


Kevin CH 寫道：

> Hi,
>
> I'm currently running into a confusion on regex and hopefully you guys
> can clear it up for me.
>
> Suppose I have a regular expression (0|(1(01*0)*1))* and two test
> strings: 110_1011101_ and _101101_1. (The underscores are not part of
> the string.  They are added to show that both string has a substring
> that matches the pattern.)  Applying a match() function on the first
> string returns true while false for the second.  The difference is the
> first one has unmatched chunk in the beginning while the second at the
> end.  How's the regex rule work here?
> 
> Thanks.