Re: Is this correct ?

On 2007-09-17, freebsd.dev@xxxxxxxxx <freebsd.dev@xxxxxxxxx> wrote:
I need to Prove that (w R)R = w for all w ??*

Where w is a string and wR is reverse of w.

As mentioned, you must prove that for all strings, of course it's not
enough just to give an example.

My crystal ball is hazy, but I suspect you have been given a formal
definition of R, something like

_R = _
where _ means an empty string,
and
(aw)R = wR a
where a is any character and w is a string - in this way one can define
the reverse of a string in terms of a slightly shorter string, etc.

Anyway, whatever formal definition of R you have been given, you
likely should use it.

(Funny how the introductory courses seem to proceed at the same pace...
I bet that in late October we'll get the pumping lemma again)

Harri H.
.

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