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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