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Re: Possreps and numeric types

From: Gene Wirchenko <genew_at_ocis.net>
Date: Thu, 29 Mar 2007 12:47:11 -0700
Message-ID: <9r5o03d81a1fra5s2qrkh9i5osdhd4vl4r@4ax.com>


Bob Badour <bbadour_at_pei.sympatico.ca> wrote:

>Gene Wirchenko wrote:
>
>> Bob Badour <bbadour_at_pei.sympatico.ca> wrote:
>>
>>>Gene Wirchenko wrote:
>>>
>>>>Bob Badour <bbadour_at_pei.sympatico.ca> wrote:
>>>>
>>>>>Gene Wirchenko wrote:
>>>>>
>>>>>>Bob Badour <bbadour_at_pei.sympatico.ca> wrote:
>>>>>>
>>>>>>[snip]
>>>>>>
>>>>>>>I admit I used epsilon somewhat sloppily and not necessarily with the
>>>>>>>exact meaning used when discussing a particular floating-point
>>>>>>>implementation. I used it to mean the distance to the representable

 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

>>>>>>>predecessor or successor of any representable rational value.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>>>>
>>>>>> That is incorrect. It is per
>>>>>> http://en.wikipedia.org/wiki/Machine_epsilon
>>>>>>In a floating-point system, epsilon is the smallest number such that
^^^^^^^^^^^^^^^^^^^^^^^^^
>>>>>> 1 + epsilon > 1
^^^^^^^^^^^^^^^
>>>>>>
>>>>>>[snip]
>>>>>
>>>>>When you say the above is incorrect, are you saying I was not using
>>>>>epsilon sloppily? Or are you saying I didn't use it to mean the distance
>>>>>to the representable predecessor or successor of any representable
>>>>>rational value?
>>>>
>>>> The definition of epsilon.
>>>
>>>Other than the "scaled by the exponent" bit, what exactly is the
>>>difference? ie. If I subtracted one from the other, what answer would I get?
>>
>> If I am understanding you, other than that difference, none. The
>> answer would be garbage.
>
>I really don't understand your objection. I noted I used the term
>sloppily and not as defined for floating point when I was discussing
>rational representations. Using the only definition I gave for the
>floating point version, the difference would be zero. The definitions
>are equivalent only stated differently.

     No. The definition that I gave is in terms of 1, not just any representatable value.

Sincerely,

Gene Wirchenko

Computerese Irregular Verb Conjugation:

     I have preferences.
     You have biases.
     He/She has prejudices.
Received on Thu Mar 29 2007 - 14:47:11 CDT

Original text of this message

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