23 May
2010
23 May
'10
12:38 p.m.
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, h . either (f, g) $ Left x = h (either (f,g) (Left x)) = h (f x) either (h . f, h . g) $ Left x = (h . f) x = h (f x) ---- h . either (f,g) $ Right y = h (either (f,g) (Right y)) = h (g y) either (h .f, h . g) $ Right y = (h . g) y = h (g y)