A Tree for TEA (tea-tree)

[rupert]

@Qqwy

The only difference between your earlier function signature and this one is the order of the first two parameters; even if one order would in practice be faster to recurse on, this does not have an impact on the order your user-facing public function have to have.

I didn’t re-order them to make it faster - I know that makes no difference.

What I am trying to say is that this signature was included to allow a more efficient implementation, the alternative would be:

updateDatum : (a -> a) -> Zipper a -> Zipper a

which means the caller must first walk a Zipper to the right location. This signature allows the Path to take a short-cut, by using the id of the datum more directly:

updateDatum : (a -> a) -> Path -> Tree a -> Tree a

I put the function a -> a first as then it becomes slightly easier to write functions for particular update operations that are then applied to specific paths and trees:

togglePath = updateDatum toggleDatum

and so on. It is quite common with map functions to put the transformation function first.