Re: comparators and "error"

[Alexey Melnikov <[e-mail]>]

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.

> 2. Even though a collation specification distinguishes between 
> "no-match" and "error", there's no requirement that all protocols 
> must. If the distinction between "no-match" and "error" is pointless 
> in e.g. sieve, can't simply sieve treat the two as equal? Ie. "match" 
> is true, "no-match" is false and "error" is false?

Yes, that is a possibility.

Maybe we should add a new match type :failedmatch which can help 
distinguish the no-match case from the error?