Haskell Strange Operator

Question

For assignment for my functional programming class, I am working on an exercise on trees. And, more specifically, on pink trees. Within the framework that we received, the data type "Rose" is already defined, but it has an operator:>. I searched him on hoogle and he said that this is the rightmost element of the sequence and the rest of the sequence. (Part of the frame below)

data Rose a = a :> [Rose a] deriving (Eq, Show) -- Exercise 1 root :: Rose a -> a root = undefined children :: Rose a -> [Rose a] children = undefined 

By no means do I want you guys to tell me how the root and children function should be executed. But if you guys can give me some tips on how to read the line “Rose a data” or maybe show me how the rosewood will grow. These things would be really great help since I enjoyed doing the exercises.

Hope someone can point me in the right direction.

Answer 1

t is very similar to a list definition:

• (:>) bit like (:)
• data Rose a = a :> [Rose a] tells you that you can get t :: Rose a
  • with element x :: a
  • and children rs :: [Rose a]
  • t = x :> rs

Of course, you can also return such elements:

 root (x :> rs) = ... 

I hope you leave everything yourself;)

Answer 2

The operator :> actually a data constructor. It would be equivalent to define the type as

 data Rose a = Node a [Rose a] 

Where (:>) = Node . So with this alternative definition you would have

 root :: Rose a -> a root (Node a subnodes) = a 

Substituting for the actual constructor :> you would have

 root ((:>) a subnodes) = a 

What can also be written as

 root (a :> subnodes) = a 

Like @Carsten says he is as a list constructor : just specialized for the Rose data type.

Answer 3

The operator :> does not have a predefined value. This is introduced by your definition of Rose, as is the identifier of Rose . In Haskell, you can define your own operators, this is one of them.

This particular operator is a data constructor that can be defined by the first character. Data constructors begin with a colon. Operators that do not start with a colon are normal functions.

It works just like any other data constructor, the only difference is that it is written in infix form, for example : In this program, it can be considered "attached to."

Since everyone can use it in their own program for any purpose, this is pointless for google.