Re: comparators and "error"

[Dave Cridland <[e-mail]>]

On Wed May 10 15:02:40 2006, Alexey Melnikov wrote:
> 
> Arnt Gulbrandsen wrote:
> 
>> I've been doing some editing on the draft, trying out how some 
>> things suggested look in prose.
>> 
>> 1. It seems useful to me that e.g. ascii-numeric can distinguish 
>> between comparing nonequal numbers and comparing out-of-scope 
>> input.
>> 
>> Take the equality operation as an example:
>> 
>> "Match" means that the collation knows how to work on the input, 
>> and the two inputs are equal as defined by the collation.
>> "No-match" means that the collation knows how, and the two are 
>> unequal.
>> "Error" means that it doesn't know how to.
>> 
>> Conflating the two latter cases smells of bad design to me, even 
>> though the difference may not be useful in every case.
> 
> I agree.
> 
> 
I'm really not so sure. On the face of it, it sounds like bad design, 
but I think there's at least two cases here - an attempt to compare 
"fish" and "bicycle", and an attempt to compare "fish" and "2". I 
have a feeling this is an important distinction.

Arguably, "fish" is equal in numeric value to "bicycle" - they both 
have no numeric value, so it's the same as comparing NIL and NIL with 
"i;octet".

Equally, "2" has a numeric value of 2, whereas "fish" does not, so 
they are unequal - like comparing NIL and an existing string with 
"i;octet".

Dave.
-- 
           You see things; and you say "Why?"
   But I dream things that never were; and I say "Why not?"
    - George Bernard Shaw