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From: stekas@hou2g.UUCP (J.STEKAS)
Newsgroups: net.puzzle
Subject: Re: Derivative of x! and actual interviews
Message-ID: <441@hou2g.UUCP>
Date: Sun, 31-Mar-85 00:29:23 EST
Article-I.D.: hou2g.441
Posted: Sun Mar 31 00:29:23 1985
Date-Received: Mon, 1-Apr-85 03:36:39 EST
References: <1337@decwrl.UUCP>, <383@cavell.UUCP>
Organization: AT&T Bell Labs, Holmdel NJ
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 From  mouli@cavell.UUCP (Bopsi Chandramouli)

> The necessary and sufficient condition for the derivative of a function
> to be defined is that the function should be continuous (and x! is not).
> Answering this question on the fly requires JUST clear thinking and good
> understanding of the fundamentals of what one has learnt before. ...

> Thus the question on derivative of x! (and other questions of similar nature)
> serves that important purpose in an interview.  

That question would weed out un-clear thinkers of the order of Ludwig
Boltzman who built statistical mechanics on the large integer limit of
the binomial distribution, [N!/(N-n)!n!].  Today we think nothing of
differentiating Poisson and Gaussian functions when we KNOW they represent
approximations of the discontinuous binomial function.

Perhaps the interviewer who used this question will one day be fortunate
enough to face an equally petty interviewer.

					Jim