Haskell自定义数据类型表达式

Question

If I have the custom data type as follows:

data MyType :: * -> *  where
Zero:: MyType a
One:: a -> MyType a
Two:: MyType a -> MyType b -> MyType (a,b)

Is it the same as writing them as:

 data MyType a = Zero
             | One a

Is the above correct? And how do I represent Two?

Answer 1

This has to be done via GADT. The trick is to enable KindSignature in your program.