Solution2.html

From HaskellWiki
Revision as of 17:49, 10 June 2013 by Prajit (talk | contribs)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search
parent :: Sheep -> Maybe Sheep
parent s = father s `mplus` mother s

grandparent :: Sheep -> Maybe Sheep
grandparent s = paternalGrandfather s `mplus` 
                paternalGrandmother s `mplus` 
                maternalGrandfather s `mplus` 
                maternalGrandmother s


This next solution will not work. If the sheep has a father and only a maternal grandparent, this function will return Nothing:

grandparent :: Sheep -> Maybe Sheep
grandparent s = parent s >>= parent