If only Haskell would let me do type MTree t = Map t (MTree t) This version work... | Hacker News

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kd0amg on April 24, 2012 | parent | context | favorite | on: One-line Tree In Python

If only Haskell would let me do

  type MTree t = Map t (MTree t)

This version works though.

  data Tree t = Leaf | Node [(t, Tree t)]

scooty-puff on April 24, 2012 [–]

The problem is that the type would be expanded indefinitely:

  Map t (Map t (Map t ...

Try:

  newtype MTree t = MTree (Map t (MTree t))

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