数组没有函子实例它看起来像scalaz
提供Functor
实例List
但Array
(或Seq
)不提供它。为什么会出现在Scalaz
scala> val fa = Functor[Array]
<console>:17: error: could not find implicit value for parameter F: scalaz.Functor[Array]
val fa = Functor[Array]
^
scala> val fl = Functor[List]
fl: scalaz.Functor[List] = [email protected]
scala> val fl = Functor[Seq]
<console>:17: error: could not find implicit value for parameter F: scalaz.Functor[Seq]
val fl = Functor[Seq]
^
这是为什么?他们不是functor吗?
请参阅我的回答[这里](http://stackoverflow.com/a/24757668/334519)关于'Seq'情况的一些讨论。 –