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Topic: Relational operators on intervals: bug?
Replies: 21   Last Post: Nov 17, 2012 3:51 AM

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Murray Eisenberg

Posts: 2,097
Registered: 12/6/04
Re: Relational operators on intervals: bug?
Posted: Nov 15, 2012 4:07 AM
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On Nov 14, 2012, at 5:39 AM, Andrzej Kozlowski <akozlowski@gmail.com> wrote:

>
> On 14 Nov 2012, at 07:28, Richard Fateman <fateman@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@math.umass.edu
Mathematics & Statistics Dept.
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University of Massachusetts 413 545-2838 (W)
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