From b53201480b92729e00b42daaf03dd60682e0f1ef Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Sun, 5 Oct 2014 09:07:05 -0700
Subject: [PATCH] remove extraneous

---
 csp/solver.rkt | 30 ++++++++++++------------------
 1 file changed, 12 insertions(+), 18 deletions(-)

diff --git a/csp/solver.rkt b/csp/solver.rkt
index 6173d4fd..54dc3bd3 100644
--- a/csp/solver.rkt
+++ b/csp/solver.rkt
@@ -28,19 +28,14 @@
     (field [_forwardcheck forwardcheck]) 
     
     (define/override (get-solution-iter domains constraints vconstraints)
-      
-      (define forwardcheck _forwardcheck)
       (define assignments (make-hash))
       (define queue null)
+      (define variable #f)
       (define values null)
       (define pushdomains null)
-      (define variable #f)
-      (define work-list null)
-      (define want-to-return #f)
-      (define return-k #f)
-      (let/ec break-loop1
-        (set! return-k break-loop1)
-        (let loop1 ()
+      (define work-list #f)
+      (let/ec return-k
+        (let main-loop ()
           ;; Mix the Degree and Minimum Remaing Values (MRV) heuristics
           (set! work-list (sort (for/list ([variable (in-hash-keys domains)])
                                   (list (* -1 (length (hash-ref vconstraints variable)))
@@ -53,7 +48,7 @@
               (set! variable last-item)
               (set! values ((hash-ref domains variable)))
               (set! pushdomains 
-                    (if forwardcheck
+                    (if _forwardcheck
                         (for/list ([x (in-hash-keys domains)] 
                                    #:when (and (not (hash-has-key? assignments x)) 
                                                (not (equal? variable x))))
@@ -69,8 +64,7 @@
               [(not (null? queue))
                (set!-values (variable values pushdomains) (pop-vvp-values! queue))
                (for-each-send pop-state pushdomains)]
-              [else
-               (set! want-to-return #t) (return-k)]))          
+              [else (return-k)]))          
           
           (let constraint-checking-loop ()
             ;; We have a variable. Do we have any values left?
@@ -78,7 +72,7 @@
               ;; No. Go back to last variable, if there is one, otherwise solver is done.
               (for/or ([i (in-naturals)])
                 (hash-remove! assignments variable)
-                (when (null? queue) (set! want-to-return #t) (return-k))
+                (when (null? queue) (return-k))
                 (set!-values (variable values pushdomains) (pop-vvp-values! queue))
                 (for-each-send pop-state pushdomains)
                 (not (null? values))))              
@@ -88,18 +82,18 @@
             (for-each-send push-state pushdomains)
             (when (for/or ([cvpair (in-list (hash-ref vconstraints variable))])
                     (match-define (list constraint variables) cvpair)
-                    (not (send constraint is-true? variables domains assignments pushdomains)))
+                    (not (send constraint broken? variables domains assignments pushdomains)))
               ;; constraint failed, so try again
               (for-each-send pop-state pushdomains) 
               (constraint-checking-loop)))
           
           ;; Push state before looking for next variable.
           (set! queue (cons (vvp variable values pushdomains) queue))
-          (loop1)))
+          (main-loop))
+        
+        (error 'get-solution-iter "Should never get here"))
       
-      (if want-to-return
-          (void)
-          (error 'get-solution-iter "Whoops, broken solver")))
+      (void))
     
     
     (define (call-solution-generator domains constraints vconstraints #:first-only [first-only #f])