DigitalGhost https://blog.hatena.ne.jp/DigitalGhost/ デ-mk6 https://dechimal.hatenadiary.com/ Haskell class Functor f => Applicative f where pure :: a->f a <*> :: f (a->b)->f a->f b class Foldable t where foldr :: (a->b->b)->b->t a->b foldr f b = foldMap (`f` b) foldMap :: Monoid m => (a->m)->t a->m foldMap f = foldr (mappend . f) mempty class (Functor t, Foldable t) => Traversable t where traverse … 190 <iframe src="https://hatenablog-parts.com/embed?url=https%3A%2F%2Fdechimal.hatenadiary.com%2Fentry%2F20091121%2F1258833081" title="Functor, Applicative, Foldable, Traversalの練習 - デ-mk6" class="embed-card embed-blogcard" scrolling="no" frameborder="0" style="display: block; width: 100%; height: 190px; max-width: 500px; margin: 10px 0px;"></iframe> Hatena Blog https://hatena.blog 2009-11-21 04:51:21 rich https://dechimal.hatenadiary.com/entry/20091121/1258833081 1.0 100%