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Re: Relational operators on intervals: bug?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg128664] Re: Relational operators on intervals: bug?
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Thu, 15 Nov 2012 03:57:15 -0500 (EST)
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  • References: <k7p3j3$ca3$1@smc.vnet.net> <20121112080708.39931690E@smc.vnet.net> <k7skt2$ku3$1@smc.vnet.net> <20121114062826.C02FC69AC@smc.vnet.net> <6F6D7B27-201F-4AC9-9553-809ABA30A7CE@mimuw.edu.pl>

On Nov 14, 2012, at 5:39 AM, Andrzej Kozlowski <akozlowski at gmail.com> wrote:

>
> On 14 Nov 2012, at 07:28, Richard Fateman <fateman at cs.berkeley.edu> wrote:
>
>> On 11/12/2012 9:13 PM, Murray Eisenberg wrote:
>>
>>>
>>> Here is the empty interval in Mathematica:
>>>
>>>  Interval[{1, 0}]
>>>
>>> Indeed:
>>>
>>>   Resolve[Exists[x, IntervalMemberQ[Interval[{1, 0}], x]]]
>>> False
>>>
>> Apparently this doesn't mean what you think it does. It gives the same
>> answer for Interval[{0,1}].
>
> Of course that is because
>
> IntervalMemberQ[Interval[{0, 1}], x]
>
> False

What remains surprising to me is:

   Resolve[Exists[x, x \[Element] Reals, IntervalMemberQ[Interval[{0, 1}], x]]]
False

---
Murray Eisenberg                           murray at math.umass.edu
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