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Topic: 3 condition in IF statement
Replies: 16   Last Post: Aug 1, 2013 12:52 PM

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Loren Shure

Posts: 977
Registered: 12/7/04
Re: 3 condition in IF statement
Posted: Aug 1, 2013 8:31 AM
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"Babak " <b_mn@hotmail.com> wrote in message
news:kt9ee8$bt7$1@newscl01ah.mathworks.com...
> "Roger Stafford" wrote in message
> <kt9dkd$a5l$1@newscl01ah.mathworks.com>...

>> "Babak " <b_mn@hotmail.com> wrote in message
>> <kt96mq$m84$1@newscl01ah.mathworks.com>...

>> > > > if ((0>=f1<=2) && (4>=f2<=5) && (1>=THD<=6))
>> - - - - - - -
>> 'Someone' is right. Strictly speaking, that notation is allowed, but
>> it is interpreted in the following remarkable way. In "4>=f2<=5" suppose
>> f2 = 6. Then the expression is parsed as:
>>
>> (4>=f2)<=5
>>
>> The "4>=f2" portion would be false which gives "false<=5", but since the
>> "<=" demands numerical values at either end, the 'false' is translated to
>> a numerical 0, which gives "0<=5" and that is actually true. However
>> this is certainly not what one would expect in such a case.
>>
>> Many people have been tripped up by this kind of unintended result.
>> The obvious remedy is to never, never use expressions of a form similar
>> to a<=b<=c in matlab.
>>
>> Roger Stafford

>
> Very interesting! Thank you for more info,nowhere I could find such info


I wrote about this on my blog last year:

http://blogs.mathworks.com/loren/2012/05/14/why-is-answer-to-3-a-7-unexpected/

--
--Loren

http://blogs.mathworks.com/loren




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