Start the SICP Huffman trees
Changes
--- a/package.lisp Mon Aug 22 20:39:20 2016 +0000
+++ b/package.lisp Tue Aug 23 00:22:20 2016 +0000
@@ -113,3 +113,15 @@
#:sand.utils)
(:export
))
+
+(defpackage #:sand.huffman-trees
+ (:use
+ #:cl
+ #:cl-arrows
+ #:losh
+ #:iterate
+ #:sand.graphviz
+ #:sand.quickutils
+ #:sand.utils)
+ (:export
+ ))
--- a/sand.asd Mon Aug 22 20:39:20 2016 +0000
+++ b/sand.asd Tue Aug 23 00:22:20 2016 +0000
@@ -40,6 +40,7 @@
(:file "markov")
(:file "dijkstra-maps")
(:file "binary-decision-diagrams")
+ (:file "huffman-trees")
(:module "terrain"
:serial t
:components ((:file "diamond-square")))
--- a/src/binary-decision-diagrams.lisp Mon Aug 22 20:39:20 2016 +0000
+++ b/src/binary-decision-diagrams.lisp Tue Aug 23 00:22:20 2016 +0000
@@ -91,6 +91,6 @@
(2 (3 0 1) 1))))
-(evaluate-bdd *maj* 1 0 1)
+; (evaluate-bdd *maj* 1 0 1)
-(draw-bdd *maj* t)
+; (draw-bdd *maj* t)
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/huffman-trees.lisp Tue Aug 23 00:22:20 2016 +0000
@@ -0,0 +1,79 @@
+(in-package #:sand.huffman-trees)
+
+(defstruct huffman-tree)
+
+(defstruct (leaf (:include huffman-tree)
+ (:constructor make-leaf (symbol weight)))
+ (symbol (required-argument))
+ (weight (required-argument) :type real))
+
+(defstruct (node (:include huffman-tree)
+ (:constructor %make-node))
+ (left (required-argument) :type huffman-tree)
+ (right (required-argument) :type huffman-tree)
+ (symbols (required-argument) :type list)
+ (weight (required-argument) :type real))
+
+
+(defun huffman-tree-symbols (tree)
+ (etypecase tree
+ (leaf (list (leaf-symbol tree)))
+ (node (node-symbols tree))))
+
+(defun huffman-tree-weight (tree)
+ (etypecase tree
+ (leaf (leaf-weight tree))
+ (node (node-weight tree))))
+
+
+(defun make-node (left right)
+ (%make-node :left left
+ :right right
+ :weight (+ (huffman-tree-weight left)
+ (huffman-tree-weight right))
+ :symbols (append (huffman-tree-symbols left)
+ (huffman-tree-symbols right))))
+
+
+(defun decode (bits tree)
+ (flet ((choose-branch (bit tree)
+ (ecase bit
+ (0 (node-left tree))
+ (1 (node-right tree)))))
+ (recursively ((bits bits)
+ (current tree))
+ (when bits
+ (let ((next-branch (choose-branch (first bits) current)))
+ (etypecase next-branch
+ (leaf (cons (leaf-symbol next-branch)
+ (recur (rest bits) tree)))
+ (node (recur (rest bits) next-branch))))))))
+
+
+(defun adjoin-set (tree set)
+ (cond
+ ((null set)
+ (list tree))
+ ((< (huffman-tree-weight tree) (huffman-tree-weight (first set)))
+ (cons tree set))
+ (t
+ (cons (first set)
+ (adjoin-set tree (rest set))))))
+
+(defun make-leaf-set (pairs)
+ (if (null pairs)
+ '()
+ (destructuring-bind (symbol weight)
+ (first pairs)
+ (adjoin-set (make-leaf symbol weight)
+ (make-leaf-set (rest pairs))))))
+
+
+(defparameter *sample-tree*
+ (make-node (make-leaf 'a 4)
+ (make-node (make-leaf 'b 2)
+ (make-node (make-leaf 'D 1)
+ (make-leaf 'C 1)))))
+
+
+; (decode '(0 1 1 0 0 1 0 1 0 1 1 1 0) *sample-tree*)
--- a/vendor/make-quickutils.lisp Mon Aug 22 20:39:20 2016 +0000
+++ b/vendor/make-quickutils.lisp Tue Aug 23 00:22:20 2016 +0000
@@ -13,6 +13,7 @@
:riffle
:tree-collect
:ensure-gethash
+ :required-argument
; :switch
; :while
; :ensure-boolean
--- a/vendor/quickutils.lisp Mon Aug 22 20:39:20 2016 +0000
+++ b/vendor/quickutils.lisp Tue Aug 23 00:22:20 2016 +0000
@@ -2,7 +2,7 @@
;;;; See http://quickutil.org for details.
;;;; To regenerate:
-;;;; (qtlc:save-utils-as "quickutils.lisp" :utilities '(:WITH-GENSYMS :ONCE-ONLY :COMPOSE :CURRY :RCURRY :N-GRAMS :DEFINE-CONSTANT :RIFFLE :TREE-COLLECT :ENSURE-GETHASH) :ensure-package T :package "SAND.QUICKUTILS")
+;;;; (qtlc:save-utils-as "quickutils.lisp" :utilities '(:WITH-GENSYMS :ONCE-ONLY :COMPOSE :CURRY :RCURRY :N-GRAMS :DEFINE-CONSTANT :RIFFLE :TREE-COLLECT :ENSURE-GETHASH :REQUIRED-ARGUMENT) :ensure-package T :package "SAND.QUICKUTILS")
(eval-when (:compile-toplevel :load-toplevel :execute)
(unless (find-package "SAND.QUICKUTILS")
@@ -18,7 +18,7 @@
:ENSURE-FUNCTION :COMPOSE :CURRY
:RCURRY :TAKE :N-GRAMS
:DEFINE-CONSTANT :RIFFLE :TREE-COLLECT
- :ENSURE-GETHASH))))
+ :ENSURE-GETHASH :REQUIRED-ARGUMENT))))
(deftype string-designator ()
"A string designator type. A string designator is either a string, a symbol,
@@ -279,8 +279,16 @@
(values value ok)
(values (setf (gethash ,key ,hash-table) ,default) nil))))
+
+ (defun required-argument (&optional name)
+ "Signals an error for a missing argument of `name`. Intended for
+use as an initialization form for structure and class-slots, and
+a default value for required keyword arguments."
+ (error "Required argument ~@[~S ~]missing." name))
+
(eval-when (:compile-toplevel :load-toplevel :execute)
(export '(with-gensyms with-unique-names once-only compose curry rcurry
- n-grams define-constant riffle tree-collect ensure-gethash)))
+ n-grams define-constant riffle tree-collect ensure-gethash
+ required-argument)))
;;;; END OF quickutils.lisp ;;;;