Hi, --- Bruno Oliveira <[EMAIL PROTECTED]> wrote:
> coerce :: a -> b > coerce x = undefined > > As an obvious consequence, Haskell type system would > be unsound. Actually, in the isomrphism, "undefined" is a proof that any theorem is correct. Somehow it can represent an assumption that a subtheorem is true (in place of a real proof -- another function). Of course, this makes "corece = undefined" rather uninteresting as a proof. > So, I assumed that this would be a wrong > interpretation. Would the following be more correct? > > ------------------------------------------ > if we can write a function: > > coerce :: a -> b > > without calling any other function or primitive > (that is, just with making use of the type system), > then this would > mean that the type system is unsound. I'd say, check what any primitive 'proves' before using it. Besides that, calling other functions is ok. Cheers, JP. __________________________________ Do you Yahoo!? Yahoo! Photos: High-quality 4x6 digital prints for 25¢ http://photos.yahoo.com/ph/print_splash _______________________________________________ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell