[Haskell] Empty instance declaration
isaacdupree at charter.net
Fri Dec 28 11:49:30 EST 2007
Ralf Laemmel wrote:
> Isaac wrote:
>> I wonder whether it would be safe for the compiler to infer simply by
>> the default methods mentioning each other in a cycle. It might miss
>> some cases when (probably involving laziness) the default methods
>> actually terminate and form an intended set of implemention, and warn
>> when it shouldn't... which is bad, but does that ever happen?
> "mentioning each other in a cycle" is too imprecise unfortunately at
> least for two reasons:
> a) we could face a well-designed mutual recursion.
> b) we could face co-induction.
I know! I said so! My question is whether anyone has an example of
doing either of those in mutually-recursive DEFAULT METHOD definitions?
sorry for yelling
You did not say anything that's imprecise about "mentioning each other
in a cycle", just the well-known fact that it's not equivalent to total
termination checking (in fact, it's neither fully an overestimate nor
underestimate of termination -- it's just an estimate that's likely to
be right when used in the context of default method definitions).
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