[Top] [All Lists]

Re: comparators and "error"

2006-05-10 10:46:32

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".

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

<Prev in Thread] Current Thread [Next in Thread>