Subject:
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RE: Would-be hacker queries. (fwd)
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 11 May 1999 14:16:31 GMT
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Original-From:
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Jim Choate <ravage@einstein(SayNoToSpam).ssz.com>
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Viewed:
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732 times
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----- Forwarded message from JR Conlin -----
Date: Tue, 11 May 1999 07:46:20 -0700
From: JR Conlin <jrconlin@email.com>
Subject: RE: Would-be hacker queries.
You know, I have never really liked the factorial example of recursion.
Honestly, how many times have you really needed to generate a factorial in
general experience?
I feel a better example is building stuff with LEGO. In this case, you are
the function and the LEGO is the data.
The basic function you perform is sticking blocks together. So to build a
rocket ship, you first need to attach the body to the engine. To build the
engine you need to attach the intake to the exhaust, and so on. As you
progress, you may be generating very complex items, but you are still
performing the same basic action, attaching one block to another.
----- End of forwarded message from JR Conlin -----
Lot's to answer your first question.
And more to the point, your example is itteration not recursion.
Recursion requires that in order to find some value (say n!) of a function we
must already know f(n-1). The power of the technique comes from its ability to
trace that chain from n > n-1 > n-2 > ... > f(1) or f(0) and then take this
value and work back up the chain. Generaly recursion is useful when it
becomes possible to describe the state of a system as a function of previous
or lower-leveled states.
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Message has 1 Reply:
 | | Re: Would-be hacker queries. (fwd)
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| (...) That is a rather limited version of recursion, which does not, in general, require f(n-1) to evaluate f(n). What you have described is actually (a subset of) partial recursion, which is provably incomplete (i.e. cannot implement some (...) (25 years ago, 12-May-99, to lugnet.robotics)
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