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

*To*: mathgroup at smc.vnet.net*Subject*: [mg82629] Re: [mg82582] Re: (x|y) \[element] Integers in Reduce function*From*: "Jean-Marc Gulliet" <jeanmarc.gulliet at gmail.com>*Date*: Fri, 26 Oct 2007 05:29:06 -0400 (EDT)*References*: <ffn0le$5sp$1@smc.vnet.net> <200710251009.GAA21790@smc.vnet.net>

Andrzej Kozlowski wrote: > On 25 Oct 2007, at 19:09, 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'). > > > > Regards, > > -- > > Jean-Marc > > > > No, the correct answer is (A) > > FullSimplify[Im[a] + Im[b], Element[a | b, Reals]] > 0 > > This only is correct when both a and b are real (given no other > knowledge of a and b). For the explanation why the answer is A and > not B see my first post in this thread. > > Andrzej Kozlowski Andrzej, Of course, you are right. I stand corrected. Best regards, -- Jean-Marc

**References**:**Re: (x|y) \[element] Integers in Reduce function***From:*Jean-Marc Gulliet <jeanmarc.gulliet@gmail.com>