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Re: (x|y) \[element] Integers in Reduce function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82582] Re: (x|y) \[element] Integers in Reduce function
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Thu, 25 Oct 2007 06:09:39 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <ffn0le$5sp$1@smc.vnet.net>

Steven Siew wrote:
> Consider the following
> 
> Reduce[x^2 - 2 y^2 == 1 && x>= 0 && y>=0 && (x|y) \[element] Integers,
> {x,y} ]
> 
> What does " (x|y) \[element] Integers "   mean?
> 
> Does it mean:
> 
> (a) x is an Integer  AND  y is an Integer
> 
> (b) x is an Integer  OR  y is an Integer

The correct answer is (b). The vertical bar | stands for *Alternatives* 
in pattern matching (equivalent to the non-exclusive logical OR). See 
ref/Alternatives and also the tutorial "Patterns Involving Alternatives" 
in the documentation center (tutorial/PatternsInvolvingAlternatives).

Note that the correct syntax for \[element] is \[Element] (with a 
capital 'e').

Regards,
-- 
Jean-Marc


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