X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=assignment4.mdwn;h=3e3b71841c6fa51e546c65c4c527cf798836de40;hp=8b8a19dc78c1b71ec20e64e6df79d8599f245755;hb=95dad38cb4aa443a3dde5bad742d53f023b0ca33;hpb=2dad468862d6fff48c8f499386dc571bd899bc28 diff --git a/assignment4.mdwn b/assignment4.mdwn index 8b8a19dc..3e3b7184 100644 --- a/assignment4.mdwn +++ b/assignment4.mdwn @@ -34,9 +34,16 @@ First, read this: [[Implementing trees]]
  1. Write an implementation of leaf-labeled trees. You can do something v3-like, or use the Y combinator, as you prefer. - You'll need an operation `make_leaf` that turns a label into a new leaf. You'll need an operation `make_node` that takes two subtrees (perhaps leaves, perhaps other nodes) and joins them into a new tree. You'll need an operation `isleaf` that tells you whether a given tree is a leaf. And an operation `extract_label` that tells you what value is associated with a given leaf. - -
  2. The **fringe** of a leaf-labeled tree is the list of values at its leaves, ordered from left to right. For example, the fringe of this tree: +You'll need an operation `make_leaf` that turns a label into a new leaf. You'll +need an operation `make_node` that takes two subtrees (perhaps leaves, perhaps +other nodes) and joins them into a new tree. You'll need an operation `isleaf` +that tells you whether a given tree is a leaf. And an operation `extract_label` +that tells you what value is associated with a given leaf. And an operation +`extract_left` that tells you what the left subtree is of a tree that isn't a +leaf. (Presumably, `extract_right` will work similarly.) + +
  3. The **fringe** of a leaf-labeled tree is the list of values at its leaves, +ordered from left to right. For example, the fringe of this tree: . / \