Subject:
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Re: A recursion question/test...
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 12 May 1999 06:27:35 GMT
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Original-From:
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Malcolm S Powell <MSP@UMBRA.COihatespam.UK>
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Viewed:
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383 times
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It should be pointed out that the problem of summing the first n natural
numbers is isomorphic to that of finding the factorial of n.
Compare these two functions
FUNCTION sum(n: natural): natural = IF n = 0 THEN 0 ELSE n + sum(n - 1)
FUNCTION fac(n: natural): natural = IF n = 0 THEN 1 ELSE n * fac(n - 1)
Only the initial conditions and the composition operators are different.
In a language that lets you enumerate sets and apply aggregate
operations to them both operations can be described trivially without
recursion (At least until you start trying to describe the axioms that
define numbers).
FUNCTION sum(n: natural): natural = PRODUCT [0..n]
FUNCTION fac(n: natural): natural = SUM [1..n]
Malcolm
> Jim Choate wrote:
>
> With all the discussion on understanding recursion and such for programmers
> I thought I'd share a little problem I find enlightening....
>
> Describe as simple a recursive algorithm as possible for summing the first n
> numbers.
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message is in Reply To:
 | | A recursion question/test...
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| Hi, With all the discussion on understanding recursion and such for programmers I thought I'd share a little problem I find enlightening.... Describe as simple a recursive algorithm as possible for summing the first n numbers. ___...___ Three step (...) (25 years ago, 12-May-99, to lugnet.robotics)
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