Re: [Haskell] semantice of seq
On Tue, 18 Jul 2006, Duncan Coutts wrote: On Tue, 2006-07-18 at 09:44 -0400, [EMAIL PROTECTED] wrote: Would the problematic semantics of seq be resolved if seq did nothing on function types? That is to say seq (\x - undefined `asTypeOf` x) y reduced to y and seq (undefined `asTypeOf` id) y also reduced to y I don't think so. You'd also have to avoid polymorphic types since they can be used at function types. Basically you'd have to bring back the Seq class. The rationale for removing the class and making seq polymorphic is mentioned in the history of Haskell draft paper that was recently advertised. I don't understand. At execution time, all the polymoric variables are gon, so we know the type of the parameter to seq. -- Russell O'Connor http://r6.ca/ ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.'' ___ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
Re: [Haskell] semantice of seq
On Wed, 2006-07-19 at 08:09 -0400, [EMAIL PROTECTED] wrote: On Tue, 18 Jul 2006, Duncan Coutts wrote: On Tue, 2006-07-18 at 09:44 -0400, [EMAIL PROTECTED] wrote: Would the problematic semantics of seq be resolved if seq did nothing on function types? That is to say seq (\x - undefined `asTypeOf` x) y reduced to y and seq (undefined `asTypeOf` id) y also reduced to y I don't think so. You'd also have to avoid polymorphic types since they can be used at function types. Basically you'd have to bring back the Seq class. The rationale for removing the class and making seq polymorphic is mentioned in the history of Haskell draft paper that was recently advertised. I don't understand. At execution time, all the polymoric variables are gon, so we know the type of the parameter to seq. Ah ok, I misunderstood. Well that'd be a bit odd too. No other function behaves differently on different types except by use of type classes. It'd make the implementations difficult too since for the rest of the language the types are not needed at runtime and so most implementations do not keep the types available at runtime. Furthermore, the fact is that seq on function types is actually useful for controlling space and time behaviour, so it's not clear that we want to ban it. Duncan ___ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
Re: [Haskell] semantice of seq
On Wed, 19 Jul 2006, Duncan Coutts wrote: Ah ok, I misunderstood. Well that'd be a bit odd too. No other function behaves differently on different types except by use of type classes. I agree it is quite odd, but the seq we have is already quite odd. Furthermore, the fact is that seq on function types is actually useful for controlling space and time behaviour, so it's not clear that we want to ban it. Do you have an example of use of seq on a function type? (Of course I don't want to ban it, just change its behaviour.) -- Russell O'Connor http://r6.ca/ ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.'' ___ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
Re: [Haskell] semantice of seq
--- [EMAIL PROTECTED] wrote: Do you have an example of use of seq on a function type? (Of course I don't want to ban it, just change its behaviour.) I don't have any wisdom to offer on how we would want to ban or change the behavior of seq on a function type without using type classes. Nor do I have an example at hand where one absolutely needs to use seq on a function type. But in any case, your request seems to be beside the point, as it comes from the assumption that only seq on function types is dangerous. But that is not true. Polymorphic use of seq can also have dire consequences when the type in question is later instantiated with, say, Int (or whatever). See numerous examples in: http://wwwtcs.inf.tu-dresden.de/~voigt/seqFinal.pdf Ciao, Janis Voigtlaender. ___ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
[Haskell] semantice of seq
Would the problematic semantics of seq be resolved if seq did nothing on function types? That is to say seq (\x - undefined `asTypeOf` x) y reduced to y and seq (undefined `asTypeOf` id) y also reduced to y -- Russell O'Connor http://r6.ca/ ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.'' ___ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
