On Sun, May 23, 2010 at 11:38 AM, Daniel Fischer <[email protected]> wrote: > On Sunday 23 May 2010 18:24:50, R J wrote: >> Correction: the theorem is >> h . either (f, g) = either (h . f, h . g) > > Still not entirely true, > > const True . either (undefined, undefined) $ undefined = True > > while > > either (const True . undefined, const True . undefined) undefined = > undefined > > But if we ignore bottom,
If we ignore bottom we say "By parametricity." The theorem is a free theorem. _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
