bits

csp/solver.rkt

@@ -78,43 +78,23 @@
             (let loop2 ()
               ;; We have a variable. Do we have any values left?
               (when (null? values)                
-                ;; No. Go back to last variable, if there's one.
-                (hash-remove! assignments variable)
-                
-               (if #f
+                ;; No. Go back to last variable, if there's one, else exit.
                 (for/or ([i (in-naturals)])
+                  (hash-remove! assignments variable)
                   (when (null? queue) (set! want-to-return #t) (return-k))
                   (set!-values (variable values pushdomains) (pop-vvp-values! queue))
                   (for-each-send pop-state pushdomains)
-                  (if (not (null? values))
-                      #t
-                      (hash-remove! assignments variable)))
-                
-                (let/ec break-loop3
-                  (let loop ()
-                    (when (null? queue)
-                      (set! want-to-return #t) 
-                      (return-k))
-                    (set!-values (variable values pushdomains) (pop-vvp-values! queue))
-                    (for-each-send pop-state pushdomains)
-                    (when (not (null? values)) (break-loop3))
-                    (hash-remove! assignments variable)
-                    (loop)))
-                )
-                )
-              
-              
+                  (not (null? values))))              
               
               ;; Got a value. Check it.
               (hash-set! assignments variable (car-pop! values))
               (for-each-send push-state pushdomains)
               (let/ec break-for-loop
-                (for ([cvpair (in-list (hash-ref vconstraints variable))])
-                  (match-define (list constraint variables) cvpair)
-                  (define the_result (send constraint call variables domains assignments pushdomains))
-                  (when (not the_result) ; Value is not good.
-                    (break-for-loop)))
-                (break-loop2))
+                (if (for/or ([cvpair (in-list (hash-ref vconstraints variable))])
+                      (match-define (list constraint variables) cvpair)
+                      (not (send constraint call variables domains assignments pushdomains)))
+                    (break-for-loop)
+                    (break-loop2)))
               
               (for-each-send pop-state pushdomains)
               (loop2)))