我有问题,在Haskell BST。 我想我已经问题定义的“钥匙”变量节点(Uzel)是奥德。但我绝对没有更多的想法。二叉搜索树,comparsion
我不过,如果我一旦确定了“关键”的说法为树类型奥德,它是有效的,并在代码中每次使用会太获取此信息。
下面的代码是不完整的,但我在谈论的东西:
data (Ord key) => Tree key value = List key value |Uzel (Tree key value) key value (Tree key value) | Null deriving (Show)
prazdny :: Ord key => Tree key value
prazdny = Null
najdi :: (Ord key,Ord k) => k -> Tree key value -> Maybe a
najdi k Null = Nothing
najdi k (Uzel levy klic hodnota pravy) = if k < klic
then najdi k levy
else najdi k pravy
当试图编译我得到这个:
bvs.hs:9:49:
Could not deduce (key ~ k)
from the context (Ord key, Ord k)
bound by the type signature for
najdi :: (Ord key, Ord k) => k -> Tree key value -> Maybe a
at bvs.hs:(8,1)-(11,58)
`key' is a rigid type variable bound by
the type signature for
najdi :: (Ord key, Ord k) => k -> Tree key value -> Maybe a
at bvs.hs:8:1
`k' is a rigid type variable bound by
the type signature for
najdi :: (Ord key, Ord k) => k -> Tree key value -> Maybe a
at bvs.hs:8:1
In the second argument of `(<)', namely `klic'
In the expression: k < klic
In the expression: if k < klic then najdi k levy else najdi k pravy
地块感谢您的想法! !
你不能用变量'klic'类型的'key'比较变量'k'类型的'k'。尝试'najdi :: Ord key =>键 - >树键值 - >可能值'作为类型(并记得有时返回一个值)。 – pigworker
事实上,该错误消息表示,'key'和'k'必须是同一类型'(键〜K)'和GHC是无法证明。 – Vitus
如果你在你的代码中使用英文名,这个问题会对更多的人更清楚。 – yairchu