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

• To: mathgroup at smc.vnet.net
• Subject: [mg82596] Re: (x|y) \[element] Integers in Reduce function
• From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
• Date: Fri, 26 Oct 2007 05:12:07 -0400 (EDT)
• Organization: The Open University, Milton Keynes, UK
• References: <ffn0le\$5sp\$1@smc.vnet.net> <ffpqjg\$lkk\$1@smc.vnet.net>

```Jean-Marc Gulliet wrote:

> 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').

In:= Element[x | y, Integers] /. {x -> 1, y -> Pi}

Out= False

In:= Element[{x, y}, Integers] /. {x -> 1, y -> Pi}

Out= False

In:= Element[x, Integers] && Element[y, Integers] /. {x -> 1,
y -> Pi}

Out= False

In:= Element[x, Integers] || Element[y, Integers] /. {x -> 1,
y -> Pi}

Out= True

Regards,
--
Jean-Marc

```

• Prev by Date: Re: Converting notebooks to use Mathematica Player
• Next by Date: Re: Selecting Rows Where All Columns Satisfy a Condition
• Previous by thread: Re: (x|y) \[element] Integers in Reduce function
• Next by thread: Re: (x|y) \[element] Integers in Reduce function