Haskell 如何计算嵌套元组的数量以及如何合并此元组列表

1.如何计算嵌套元组的数量

2.合并时出错，即使嵌套数相同，如何合并此元组列表

错误：

<interactive>:13:1:
    No instance for (Eq Expr) arising from a use of `union'
    Possible fix: add an instance declaration for (Eq Expr)
    In the expression: union b1 b2
    In an equation for `it': it = union b1 b2

此处的函数定义与声明不一致。但这不仅仅是一个错误：您调用的“tuple”实际上是一个树，因此您可能需要这样的代码：

data NestType = ConsLeaf Int | ConsPair NestType NestType

countnest :: NestType -> Int
countnest (ConsLeaf _) = 1
countnest (ConsPair x y) = max (countnest x) (countnest y) +1

---

如果定义自定义类型，它就不再是元组了。可以直接计算元组吗？此外，在上述情况下，b1和b2如何合并？如何使用此自定义类型？countnest（ConsPair（ConsLeaf 1）（ConsLeaf 2））（ConsLeaf 3））我现在知道如何使用您的意思是“union”是连接吗？（1,2,3）->[1,2,3]？在更改此数据表达式时遇到了一些困难，即导出（显示）数据NestType=ConsLeaf Expr | ConsPair NestType让cartProd xs ys=[（ConsPair（ConsLeaf x），（ConsLeaf y））| x并集是串联的[（1,2），3]（（4,5），6）]到[（1,2），3），（4,5）]

*Main> :l oo.hs
[1 of 1] Compiling Main             ( oo.hs, interpreted )

oo.hs:140:12:
    Couldn't match expected type `Int'
                with actual type `((Int, Int), (Int, Int))'
    In the pattern: (a1, a2)
    In the pattern: ((a1, a2), (b1, b2))
    In an equation for `countnest':
        countnest ((a1, a2), (b1, b2))
          = max
              (max
                 ((countnest (fst (a1, a2))) + 1) ((countnest (snd (a1, a2))) + 1))
              (max
                 ((countnest (fst (b1, b2))) + 1) ((countnest (snd (b1, b2))) + 1))

oo.hs:140:21:
    Couldn't match expected type `Int'
                with actual type `((Int, Int), (Int, Int))'
    In the pattern: (b1, b2)
    In the pattern: ((a1, a2), (b1, b2))
    In an equation for `countnest':
        countnest ((a1, a2), (b1, b2))
          = max
              (max
                 ((countnest (fst (a1, a2))) + 1) ((countnest (snd (a1, a2))) + 1))
              (max
                 ((countnest (fst (b1, b2))) + 1) ((countnest (snd (b1, b2))) + 1))

countnest :: (Int,Int) -> Int
countnest ((a1,a2), (b1,b2)) = ...

data NestType = ConsLeaf Int | ConsPair NestType NestType

countnest :: NestType -> Int
countnest (ConsLeaf _) = 1
countnest (ConsPair x y) = max (countnest x) (countnest y) +1