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Task/Zebra-puzzle/EchoLisp/zebra-puzzle-1.echolisp

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+(lib 'hash)
+(lib 'amb)
+
+;; return #f or house# for thing/category
+;; houses := (0 1 2 3 4)
+(define (house-get H  category thing houses)
+        (for/or ((i houses)) #:continue (!equal? (hash-ref (vector-ref H i) category) thing)
+        i))
+
+ ;; return house # for thing (eg cat) in category (eq animals)
+ ;; add thing if not already here
+(define-syntax-rule (house-set thing category)
+    	(or
+    	 (house-get H 'category 'thing houses)
+         (dispatch H 'category 'thing context houses )))
+
+;; we know that thing/category is in a given house
+(define-syntax-rule (house-force thing category house)
+        (dispatch H 'category 'thing context houses  house))
+
+;; return house# or fail if impossible
+(define (dispatch H category thing  context houses  (forced #f))
+        (define house (or forced  (amb context houses))) ;; get a house number
+        (when (hash-ref (vector-ref H house) category) (amb-fail)) ;; fail if occupied
+        (hash-set (vector-ref H house) category thing) ;; else remember house contents
+        house)
+
+(define (house-next h1 h2)
+ 	(amb-require (or (= h1 (1+ h2)) (= h1 (1- h2)))))
+	
+(define (zebra-puzzle context houses  )
+    (define H (build-vector 5 make-hash)) ;; house[i] :=  hash(category) -> thing
+; In the middle house they drink milk.
+    (house-force milk drinks 2)
+;The Norwegian lives in the first house.
+    (house-force norvegian people 0)
+;  The English man lives in the red house.
+    (house-force red colors(house-set english people))
+; The Swede has a dog.
+    (house-force dog animals (house-set swede people))
+;  The Dane drinks tea.
+    (house-force tea drinks (house-set dane people))
+;  The green house is immediately to the left of the white house.
+   (amb-require (=   (house-set green colors) (1- (house-set white colors))))
+;  They drink coffee in the green house.
+    (house-force coffee drinks (house-set green colors))
+;  The man who smokes Pall Mall has birds.
+    (house-force birds  animals (house-set pallmall smoke))
+;  In the yellow house they smoke Dunhill.
+    (house-force dunhill smoke (house-set yellow colors))
+;  The Norwegian lives next to the blue house.
+    (house-next (house-set norvegian people) (house-set blue colors))
+;  The man who smokes Blend lives in the house next to the house with cats.
+    (house-next (house-set blend smoke) (house-set cats  animals))
+; In a house next to the house where they have a horse, they smoke Dunhill.
+    (house-next (house-set horse animals) (house-set dunhill smoke))
+; The man who smokes Blue Master drinks beer.
+    (house-force beer drinks (house-set bluemaster smoke))
+; The German smokes Prince.
+    (house-force prince smoke (house-set german people))
+; They drink water in a house next to the house where they smoke Blend.
+    (house-next (house-set water drinks) (house-set blend smoke))
+
+;; Finally .... the zebra 🐴
+    (house-set 🐴 animals)
+
+    (for ((i houses))
+    (writeln i (hash-values (vector-ref H i))))
+    (writeln '----------)
+
+    (amb-fail) ;; will ensure ALL solutions are printed
+)

Task/Zebra-puzzle/EchoLisp/zebra-puzzle-2.echolisp

@@ -0,0 +1,12 @@
+(define (task)
+    (amb-run zebra-puzzle  (amb-make-context) (iota 5)))
+
+(task)
+   →
+0     (norvegian yellow dunhill cats water)
+1     (dane tea blue blend horse)
+2     (milk english red pallmall birds)
+3     (green coffee german prince 🐴)
+4     (swede dog white bluemaster beer)
+----------
+  → #f