Comments: Fix add1Tree cursorize example

[vidsinghal]

No description provided.

[ulysses4ever]

Suggested change

	if the functions "traverses" it's input (more details in the paper).
	if the functions "traverses" its input (more details in the paper).

[ulysses4ever]

One day we'll add doctests, and all those commented out examples will be checked... I hope!

[vidsinghal]

To introduce the notion of mutable cursors, would it not be ideal if we just change lout in the example to a mutable cursor since we still want the read cursors to be non-mutable @rrnewton ?
Continuing the example in the Cursorize file.

E.g.

    add1Tree :: Tree -> Tree
    add1Tree tr =
      case tr of
        Leaf n   -> Leaf (n + 1)
        Node l r -> Node (add1Tree l) (add1Tree r)

becomes

    -- char*
    type Cursor = Ptr Char

    add1Tree :: Cursor -> Cursor -> Cursor -> Cursor -> (Cursor,Cursor,Cursor,(Cursor,Cursor))
    add1Tree end_rin end_rout lout lin =
      in case lin of
           Leaf -> let n = readScalar "Int" (lin + 1) 
                       wt = writeTag lout Leaf
                       wi = writeInt wt (n+1)
                   in (lin + 9, (lout, wi))
           Node -> ...

For mutable cursor case, this potentially turns into something like

    -- char*
    type Cursor = Ptr Char
    -- char**
    type MutableCursor = Ptr Ptr Char

    add1Tree :: Cursor -> Cursor -> MutableCursor -> Cursor -> (Cursor,Cursor)
    add1Tree end_rin end_rout lout lin =
      in case lin of
           Leaf -> let n = readScalar "Int" (lin + 1) 
                       wt = writeTag lout Leaf
                       wi = writeInt wt (n+1)
                   in (lout, wi)
           Node -> ...

For the return type, there are 2 possibilities, we could still return the start location and end location of the Packed type (Cursor,Cursor) or make the function a void function.
For the former it might require to pass another argument to thread the start location of the output buffer, in which case it seems like making it void is probably better.