Re: Why does MemberQ[{0,1,2}, expr_] evaluate to True?
- To: mathgroup at smc.vnet.net
- Subject: [mg125913] Re: Why does MemberQ[{0,1,2}, expr_] evaluate to True?
- From: Christoph Lhotka <christoph.lhotka at fundp.ac.be>
- Date: Fri, 6 Apr 2012 06:01:55 -0400 (EDT)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
- References: <4F7D8716.4010202@fundp.ac.be>
I am really sorry for reposting it but of course the subject of discussion should be: MemberQ[{0, 1, 2}, expr_] Please replace below and in message ModuleQ by MemberQ. best, christoph On 04/05/2012 01:50 PM, Christoph Lhotka wrote: > Hello, > > I found and interesting subject of discussion in the post > > "Bug in pattern test, or I did something wrong?" > > > I could trace back the problem to an issue with ModuleQ. > > Question: Why does > > In[12]:= ModuleQ[{0,1,2},expr_] > > Out[12]:= True > > evaluate to True? > > > My argumentation is as follows: > > On the one hand there could be a chance that expr_ is 0,1 or 2 but on > the other > hand the probability that expr_ is not 0,1 or 2 is even higher. As a > conclusion it should neither > evaluate to True nor to False. > > In other words: Is there any reason why the expression of everything > (named expr) > is contained in the set {0,1,2} ? > > Best, > > Christoph