On 2010-01-07 20:48, Juergen Schoenwaelder wrote:
> On Thu, Jan 07, 2010 at 03:18:43AM +0100, Brian E Carpenter wrote:
>
>> Surely we can never hope to eliminate the need for converting to a
>> a canonical form before comparing. The canonical form for machine
>> comparisons is fairly obvious - a 128 bit binary number. The question
>> seems to be whether we can define a canonical form for eyeball comparisons.
>
>> I thought the idea of this work was to help humans by minimising the
>> variability in the "printed" version of an address.
>
> The motivation is not just eyeball comparison by humans as explained
> in section 3 of the ID. IP addresses are stored in many places in a
> textual form where the options of automated search and comparison are
> textual and conversion to a 128-bit binary number for comparison is
> often not a realistic option. Section 3 of the ID discusses some
> examples.
Well, any attempt to make arbitrary text comparisons 100% reliable is
logically excluded by the first paragraph of section 4.
For reliable text-to-text comparisons you have no choice but to
convert to a strict canonical form, and that surely means converting
dotted decimal to hex, if you can't convert to binary.
Brian
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