Testing: modify parse to just take a verb phrase

This was done to test the alternative parse-verb-phrase.

mceval/amb-natural-language.rkt

@@ -1,75 +1,95 @@
 (define nouns '(noun student professor cat class))
-
 (define verbs '(verb studies lectures eats sleeps))
-
 (define articles '(article the a))
+(define prepositions '(prep for to in by with))
 
-;; output of parse
-'(sentence (noun-phrase (article the) (noun cat))
-           (verb eats))
+(define (log message level)
+  (define (output message level)
+    (if (= level 0) message
+        (cons '_ (output message (- level 1)))))
+  (display (output message level))
+  (newline))
 
-(define (parse-sentence)
-  (list 'sentence
-         (parse-noun-phrase)
-         (parse-word verbs)))
-
-(define (parse-noun-phrase)
-  (list 'noun-phrase
-        (parse-word articles)
-        (parse-word nouns)))
-
-(define (parse-word word-list)
+(define (parse-word word-list level)
+  (log (list 'word-list word-list '*unparsed* *unparsed*) level)
   (require (not (null? *unparsed*)))
   (require (memq (car *unparsed*) (cdr word-list)))
   (let ((found-word (car *unparsed*)))
     (set! *unparsed* (cdr *unparsed*))
+    (log (list (car word-list) found-word) level)
     (list (car word-list) found-word)))
 
 (define *unparsed* '())
 
 (define (parse input)
   (set! *unparsed* input)
-  (let ((sent (parse-sentence)))
+  (let ((sent (parse-verb-phrase 0)))
     (require (null? *unparsed*))
     sent))
 
-
-;: (parse '(the cat eats))
-;; output of parse
-'(sentence (noun-phrase (article the) (noun cat)) (verb eats))
-
-(define prepositions '(prep for to in by with))
-
-(define (parse-prepositional-phrase)
-  (list 'prep-phrase
-        (parse-word prepositions)
-        (parse-noun-phrase)))
-
 (define (parse-sentence)
   (list 'sentence
-         (parse-noun-phrase)
-         (parse-verb-phrase)))
+         ;;(parse-noun-phrase)
+         (parse-verb-phrase 0)))
 
-(define (parse-verb-phrase)
+(define (parse-noun-phrase level)
+  (define (maybe-extend noun-phrase)
+    (log '(maybe-extend-noun) level)
+    (amb (begin
+           (log '(amb-noun-phrase) level)
+           noun-phrase)
+         (begin
+           (log '(amb-maybe-extend-noun) level)
+           (maybe-extend (list 'noun-phrase
+                               noun-phrase
+                               (parse-prepositional-phrase level))))))
+  (log '(parse-noun-phrase) level)
+  (maybe-extend (parse-simple-noun-phrase (+ level 1))))
+
+;; Note maybe-extend is tail recursive
+(define (parse-verb-phrase level)
   (define (maybe-extend verb-phrase)
+    (log '(maybe-extend-verb-phrase) level)
     (amb verb-phrase
          (maybe-extend (list 'verb-phrase
                              verb-phrase
-                             (parse-prepositional-phrase)))))
-  (maybe-extend (parse-word verbs)))
+                             (parse-prepositional-phrase level)))))
+  (log '(parse-verb-phrase) level)
+  (maybe-extend (parse-word verbs level)))
 
-(define (parse-simple-noun-phrase)
+(define (parse-simple-noun-phrase level)
+  (log '(parse-simple-noun) level)
   (list 'simple-noun-phrase
-        (parse-word articles)
-        (parse-word nouns)))
+        (parse-word articles level)
+        (parse-word nouns level)))
+
+(define (parse-prepositional-phrase level)
+  (log '(parse-prep) level)
+  (list 'prep-phrase
+        (parse-word prepositions level)
+        (parse-noun-phrase level)))
+
+
+
+;; Note: not tail recursive
+(define (parse-verb-phrase level)
+  (log '(parse-verb-phrase) level)
+  (amb (begin
+         (log '(amb-parse-verbs) level)
+         (parse-word verbs level))
+       (begin
+         (log '(amb-verb-prep) level)
+         (list 'verb-phrase
+               (parse-verb-phrase (+ level 1))
+               (parse-prepositional-phrase level)))))
+
+
+
+
+
+
+
 
-(define (parse-noun-phrase)
-  (define (maybe-extend noun-phrase)
-    (amb noun-phrase
-         (maybe-extend (list 'noun-phrase
-                             noun-phrase
-                             (parse-prepositional-phrase)))))
-  (maybe-extend (parse-simple-noun-phrase)))
 
 
 ;; Exercise 4.45: Output of (parse '(the professor lectures to the student in the class with the cat))