regexp question

[PhilipNienhuis]

I need to check if a string contains one or more sequences of exactly two
identical consecutive characters.
So I figured I could do (in Octave-3.4.3 MinGW), e.g.:

octave:1> tststr = 'baaaaa baab'
tststr = baaaaa baab
octave:2> regexp (tststr, "a{2}")

but the result is:

ans =
   2   4   9

which -depending on perception- may be right but intuitively is not what I
expected (uhm, hoped).
I'd expect the first sequence of five consecutive "a"s to be indexed only
with a pattern of "a{5}" but obviously I'm wrong.

Now, the "aaaaa" substring actually contains 4 "aa" sequences, so regexp's
choice is at least a bit arbitrary; I couldn't find in the docs that regexp
only returns non-overlapping substring patterns.
IMO strfind() does this more consistently:

octave:12> strfind (tststr, 'aa')
ans =
   2   3   4   5   9


Anyway:

Q1: Just to be sure: IS this the way regexp() is supposed to work?

Q2: Of course: how can I get together what I'm after? i.e., to find only the
position of the one "aa" substring in tststr starting at position 9?

Thanks,

Philip


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