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- (define-module (tree)
- ;; The exported procedures are created from the macro which defines record
- ;; types, where one cannot use define-public.
-
- make-split
- split?
- split-feature-index
- split-value
- set-split-value
- split-subsets
- set-split-subsets
- split-cost
- set-split-cost
- Node
- make-node
- node?
- node-data
- set-node-data
- node-split-feature-index
- set-node-split-feature-index
- node-split-value
- set-node-split-value
- node-left
- set-node-left
- node-right
- set-node-right))
- (use-modules
- ;; SRFI-9 for standardized records
- (srfi srfi-9)
- ;; for functional structs (not part of srfi-9 directly)
- (srfi srfi-9 gnu)
- (utils display)
- (utils string)
- (dataset))
- ;; ===============
- ;; DATA STRUCTURES
- ;; ===============
- ;; A Split record is simply a structure to contain all information about a
- ;; split. It is not a node containing data.
- (define-immutable-record-type Split
- ;; define constructor
- (make-split index value subsets cost)
- ;; define predicate
- split?
- ;; define accessors and functional setters
- ;; Note: It should never be required to update the index of the feature, which
- ;; was used to create the split. If that feature changed, the whole split
- ;; record would become invalid and a new instance should be created.
- (index split-feature-index)
- (value split-value set-split-value)
- (subsets split-subsets set-split-subsets)
- (cost split-cost set-split-cost))
- ;; A Node record is a node of the decision tree. It contains data and
- ;; information about the feature, at which it splits and the value for that
- ;; split. It also contains references to the child nodes.
- (define-immutable-record-type Node
- ;; define constructor
- (make-node data split-feature-index split-value left right)
- ;; define predicate
- node?
- ;; define accessors and functional setters
- (data node-data set-node-data)
- (split-feature-index
- node-split-feature-index
- set-node-split-feature-index)
- (split-value
- node-split-value
- set-node-split-value)
- (left node-left set-node-left)
- (right node-right set-node-right))
- (define-public make-leaf-node
- (lambda (data)
- (make-node data
- 'none
- 'none
- empty-dataset
- empty-dataset)))
- (define-public make-leaf-node-from-split-node
- (lambda (split-node)
- (make-leaf-node (node-data split-node))))
- (define-public leaf-node?
- (lambda (node)
- (and (dataset-empty? (node-left node))
- (dataset-empty? (node-right node)))))
- (define-public last-split-node?
- (lambda (node)
- (cond [(leaf-node? node)
- [else
- (and (leaf-node? (node-left node))
- (leaf-node? (node-right node)))])))
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