Regular Expression: Matching substring

[Kevin CH]

Oh yea, I see what's my confusion now.  In the first string, I didn't
consider 11 and 0 matches the pattern without the repetition.  Actually
what I did is I entered the pattern and the test strings into kudos (a
python regexp debugger) and got the match groups, which didn't have 11
and 0 as matches, although they do match the pattern "(0|1(01*0)*1)".

Thank you for the help.


Leon wrote:
> You are right. In fact the procedure is as follows:
> The substr ``101101" is no problem, if stop here, match will
> successful.
> But the tailing `1' occurs, so we may imagine the working automata move
> to a state, which according to the regexp's outer most `)', and ready
> to repeat
> the whole regexp again. In this case, the answer is ``yes" only when
> there exists
> at least two ``1", but only one here.
>
> BTW, the first string is matched exactly, according to your notion, it
> should be written as: _11_0_1011101