Resolve the issue that caused the amb language parser to fail and figure out how to get multiple amb-solutions

ex-4_35-44.scm

@@ -100,15 +100,37 @@
 (my-assert (multiple-dwelling)
            '((baker 3) (cooper 2) (fletcher 4) (miller 5) (smith 1)))
 
+(define (multiple-dwelling-removed)
+  (let ((baker (amb 1 2 3 4 5))
+        (cooper (amb 1 2 3 4 5))
+        (fletcher (amb 1 2 3 4 5))
+        (miller (amb 1 2 3 4 5))
+        (smith (amb 1 2 3 4 5)))
+    (require (distinct? (list baker cooper fletcher miller smith)))
+    (require (not (= baker 5)))
+    (require (not (= cooper 1)))
+    (require (not (= fletcher 5)))
+    (require (not (= fletcher 1)))
+    (require (> miller cooper))
+    ;; (require (not (= (abs (- smith fletcher)) 1))) ; adjacent floors constraint
+    (require (not (= (abs (- fletcher cooper)) 1)))
+    (list (list 'baker baker)
+          (list 'cooper cooper)
+          (list 'fletcher fletcher)
+          (list 'miller miller)
+          (list 'smith smith))))
+
 ; There are five solutions when the adjacent floor constraint for smith and
 ; fletcher is removed.
 
+(my-assert (length (set-of (multiple-dwelling-removed))) 5)
+
 (display "\nex-4.39 - multiple-dwelling-ordering\n")
 
 ; The ordering does not matter because the interpreter first evaluates all ambs
 ; and then runs the checks. The interpreter will check all combinations even if
 ; they cannot yield a possible solution, such as (fletcher 1). To avoid this one
-; would have to interleave the am expression and the checks.
+; would have to interleave the amb expression and the checks.
 
 (display "[answered]\n")
 
@@ -216,6 +238,20 @@
 
 (display "\nex-4.42 - liars-puzzle\n")
 
+;    Five schoolgirls sat for an examination. Their parents -- so they thought
+;    -- showed an undue degree of interest in the result. They therefore agreed
+;    that, in writing home about the examination, each girl should make one
+;    true statement and one untrue one. The following are the relevant passages
+;    from their letters:
+;
+;        Betty: ``Kitty was second in the examination. I was only third.''
+;        Ethel: ``You'll be glad to hear that I was on top. Joan was second.''
+;        Joan: ``I was third, and poor old Ethel was bottom.''
+;        Kitty: ``I came out second. Mary was only fourth.''
+;        Mary: ``I was fourth. Top place was taken by Betty.''
+;
+;    What in fact was the order in which the five girls were placed?
+
 (define (no-violation new-stmt stmts)
   (if (null? stmts)
     #t
@@ -330,4 +366,5 @@
   (queens-iter '() 8))
 
 (my-assert (queens) '(4 2 7 3 6 8 5 1))
+(my-assert (length (set-of (queens))) 92)