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Why does ModuleQ[{0,1,2}, expr_] evaluate to True?

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  • Subject: [mg125912] Why does ModuleQ[{0,1,2}, expr_] evaluate to True?
  • From: Christoph Lhotka <christoph.lhotka at>
  • Date: Fri, 6 Apr 2012 06:01:34 -0400 (EDT)
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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} ?



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