From f06623c0702f31497854f7316f3045b0e9746890 Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Fri, 26 Oct 2018 14:10:57 -0700
Subject: [PATCH] nits

---
 csp/csp/hacs.rkt      | 115 +++++++++++++------------
 csp/csp/sudoku-jm.rkt | 193 ++++++++++++++++++------------------------
 2 files changed, 143 insertions(+), 165 deletions(-)

diff --git a/csp/csp/hacs.rkt b/csp/csp/hacs.rkt
index 806c842c..74114634 100644
--- a/csp/csp/hacs.rkt
+++ b/csp/csp/hacs.rkt
@@ -73,19 +73,23 @@
   (() ((listof var?) (listof constraint?)) . ->* . csp?)
   (csp vars consts))
 
+(define/contract (make-var name [vals null])
+  ((name?) ((listof any/c)) . ->* . var?)
+  (var name vals))
+
 (define/contract (add-vars! prob names-or-procedure [vals-or-procedure empty])
   ((csp? (or/c (listof name?) procedure?)) ((or/c (listof any/c) procedure?)) . ->* . void?)
   (for/fold ([vrs (vars prob)]
-             #:result (set-csp-vars! prob vrs))
+             #:result (set-csp-vars! prob (reverse vrs)))
             ([name (in-list (match names-or-procedure
                               [(? procedure? proc) (proc)]
                               [names names]))])
     (when (memq name (map var-name vrs))
       (raise-argument-error 'add-vars! "var that doesn't already exist" name))
-    (append vrs (list (var name
-                           (if (procedure? vals-or-procedure)
-                               (vals-or-procedure)
-                               vals-or-procedure))))))
+    (cons (make-var name
+                    (match vals-or-procedure
+                      [(? procedure? proc) (proc)]
+                      [vals vals])) vrs)))
 
 (define/contract (add-var! prob name [vals-or-procedure empty])
   ((csp? name?) ((or/c (listof any/c) procedure?)) . ->* . void?)
@@ -206,33 +210,34 @@
 
 (define/contract (assign-val prob name val)
   (csp? name? any/c . -> . csp?)
-  (when-debug (set! nassns (add1 nassns)))
-  (make-csp
-   (for/list ([vr (in-vars prob)])
-     (if (eq? name (var-name vr))
-         (assigned-var name (list val))
-         vr))
-   (constraints prob)))
-
-(define/contract (assigned-vars prob)
-  (csp? . -> . (listof var?))
-  (filter assigned-var? (vars prob)))
+  (begin0
+    (make-csp
+     (for/list ([vr (in-vars prob)])
+       (if (eq? name (var-name vr))
+           (assigned-var name (list val))
+           vr))
+     (constraints prob))
+    (when-debug (set! nassns (add1 nassns)))))
+
+(define/contract (assigned-vars prob [invert? #f])
+  ((csp?) (any/c) . ->* . (listof var?))
+  ((if invert? filter-not filter) assigned-var? (vars prob)))
 
 (define/contract (unassigned-vars prob)
   (csp? . -> . (listof var?))
-  (filter-not assigned-var? (vars prob)))
+  (assigned-vars prob 'invert))
 
 (define/contract (first-unassigned-variable csp)
   (csp? . -> . (or/c #false (and/c var? (not/c assigned-var?))))
   (match (unassigned-vars csp)
-    [(? empty?) #false]
+    [(== empty) #false]
     [xs (first xs)]))
 
 (define/contract (argmin* proc xs [max-style? #f])
   ((procedure? (listof any/c)) (any/c) . ->* . (listof any/c))
   ;; return all elements that have min value.
   (match xs
-    [(? empty?) xs]
+    [(== empty) xs]
     [(list x) xs]
     [xs
      (define vals (map proc xs))
@@ -250,13 +255,13 @@
 (define/contract (minimum-remaining-values prob)
   (csp? . -> . (or/c #false (and/c var? (not/c assigned-var?))))
   (match (unassigned-vars prob)
-    [(? empty?) #false]
+    [(== empty) #false]
     [uvars (random-pick (argmin* domain-length uvars))]))
 
 (define/contract (max-degree prob)
   (csp? . -> . (or/c #false (and/c var? (not/c assigned-var?))))
   (match (unassigned-vars prob)
-    [(? empty?) #false]
+    [(== empty) #false]
     [uvars (random-pick (argmax* (λ (var) (var-degree prob var)) uvars))]))
 
 (define mrv minimum-remaining-values)
@@ -279,7 +284,7 @@
 (define/contract (mrv-degree-hybrid prob)
   (csp? . -> . (or/c #f var?))
   (match (unassigned-vars prob)
-    [(? empty?) #false]
+    [(== empty) #false]
     [uvars
      (max-degree (make-csp (argmin* domain-length uvars) (constraints prob)))]))
   
@@ -326,9 +331,9 @@
      (cond
        [(assigned-var? vr) vr]
        [(eq? name (var-name vr))
-        (var name (match (filter satisfies-arc? (domain vr))
-                    [(? empty?) (backtrack!)]
-                    [vals vals]))]
+        (make-var name (match (filter satisfies-arc? (domain vr))
+                         [(? empty?) (backtrack!)]
+                         [vals vals]))]
        [else vr]))
    (constraints prob)))
 
@@ -472,10 +477,10 @@
        (for/list ([vr (in-vars prob)])
          (match-define (var name vals) vr)
          (define name-constraints (filter (λ (const) (constraint-relates? const name)) unary-constraints))
-         (var name (for/list ([val (in-list vals)]
-                              #:when (for/and ([const (in-list name-constraints)])
-                                       ((constraint-proc const) val)))
-                     val)))
+         (make-var name (for/list ([val (in-list vals)]
+                                   #:when (for/and ([const (in-list name-constraints)])
+                                            ((constraint-proc const) val)))
+                          val)))
        other-constraints)))
 
 (define ((make-hist-proc assocs) . xs)
@@ -494,32 +499,32 @@
   (generator ()
              (define reduce-arity-proc (if (current-arity-reduction) reduce-constraint-arity values))
              (let loop ([prob ((if (current-node-consistency) make-nodes-consistent values) prob)])
-                 (match (select-unassigned-variable prob)
-                   [#false (yield prob)]
-                   [(var name domain)
-                    (define (wants-backtrack? exn)
-                      (and (backtrack? exn) (or (let ([bths (backtrack-histories exn)])
-                                                  (or (empty? bths) (for*/or ([bth bths]
-                                                                              [rec bth])
-                                                                      (eq? name (car rec))))))))
-                    (for/fold ([conflicts null]
-                               #:result (void))
-                              ([val (in-list (order-domain-values domain))])
-                      (with-handlers ([wants-backtrack?
-                                       (λ (bt)
-                                         (define bths (backtrack-histories bt))
-                                         (append conflicts (remq name (remove-duplicates
-                                                                       (for*/list ([bth bths]
-                                                                                   [rec bth])
-                                                                         (car rec)) eq?))))])
-                        (let* ([prob (assign-val prob name val)]
-                               ;; reduce constraints before inference,
-                               ;; to create more forward-checkable (binary) constraints
-                               [prob (reduce-arity-proc prob)]
-                               [prob (inference prob name)]
-                               [prob (check-constraints prob)])
-                          (loop prob)))
-                      conflicts)]))))
+               (match (select-unassigned-variable prob)
+                 [#false (yield prob)]
+                 [(var name domain)
+                  (define (wants-backtrack? exn)
+                    (and (backtrack? exn) (or (let ([bths (backtrack-histories exn)])
+                                                (or (empty? bths) (for*/or ([bth bths]
+                                                                            [rec bth])
+                                                                    (eq? name (car rec))))))))
+                  (for/fold ([conflicts null]
+                             #:result (void))
+                            ([val (in-list (order-domain-values domain))])
+                    (with-handlers ([wants-backtrack?
+                                     (λ (bt)
+                                       (define bths (backtrack-histories bt))
+                                       (append conflicts (remq name (remove-duplicates
+                                                                     (for*/list ([bth bths]
+                                                                                 [rec bth])
+                                                                       (car rec)) eq?))))])
+                      (let* ([prob (assign-val prob name val)]
+                             ;; reduce constraints before inference,
+                             ;; to create more forward-checkable (binary) constraints
+                             [prob (reduce-arity-proc prob)]
+                             [prob (inference prob name)]
+                             [prob (check-constraints prob)])
+                        (loop prob)))
+                    conflicts)]))))
 
 (define/contract (random-pick xs)
   ((non-empty-listof any/c) . -> . any/c)
diff --git a/csp/csp/sudoku-jm.rkt b/csp/csp/sudoku-jm.rkt
index 4f13cdb2..62ab9c32 100644
--- a/csp/csp/sudoku-jm.rkt
+++ b/csp/csp/sudoku-jm.rkt
@@ -1,4 +1,4 @@
-#lang racket/base
+#lang debug racket/base
 (require racket/match
          racket/list
          racket/set)
@@ -25,43 +25,18 @@
   (= (cell-y l) (cell-y r)))
 
 ;; a grid is a list of cells
-
-(define hrule "-----------")
-
 ;; board : string ... -> grid
 (define (board . ss)
-  (match-define
-   (list r1 r2 r3 (== hrule)
-         r4 r5 r6 (== hrule)
-         r7 r8 r9)
-   ss)
-  (define rs
-    (list r1 r2 r3 r4 r5 r6 r7 r8 r9))
-  (flatten
-   (for/list ([r (in-list rs)]
-              [y (in-naturals)])
-     (parse-row y r))))
+  (for*/fold ([cells null]
+              #:result (reverse cells))
+             ([str (in-list ss)]
+              [c (in-port read-char (open-input-string str))]
+              #:unless (memv c '(#\- #\|)))
+    (define-values (row col) (quotient/remainder (length cells) 9))
+    (cons (cell col row (cond
+                          [(string->number (string c)) => seteq]
+                          [else anything])) cells)))
 
-(define (parse-row y r)
-  (for/list ([c (in-string r)]
-             [i (in-naturals)])
-    (cond
-      [(or (= i 3) (= i 7))
-       (if (char=? c #\|)
-         empty
-         (error 'parse-row))]
-      [else
-       (define x
-         (cond [(< i 3) (- i 0)]
-               [(< i 7) (- i 1)]
-               [   else (- i 2)]))
-       (parse-cell y x c)])))
-
-(define (parse-cell y x c)
-  (cell x y
-        (if (char=? #\space c)
-          anything
-          (seteq (string->number (string c))))))
 
 (define (propagate-one top cs)
   (let/ec return
@@ -69,7 +44,7 @@
     (when (cell-solved? top)
       (define-values (changed? ncs)
         (for/fold ([changed? #f] [ncs empty])
-            ([c (in-list cs)])
+                  ([c (in-list cs)])
           (cond
             [(neighbor-of? top c)
              (define before
@@ -78,12 +53,12 @@
                (set-subtract before (cell-can-be top)))
              (if (= (set-count before)
                     (set-count after))
-               (values changed?
-                       (cons c ncs))
-               (values #t
-                       (cons (struct-copy cell c
-                                          [can-be after])
-                             ncs)))]
+                 (values changed?
+                         (cons c ncs))
+                 (values #t
+                         (cons (struct-copy cell c
+                                            [can-be after])
+                               ncs)))]
             [else
              (values changed? (cons c ncs))])))
       (return changed? top ncs))
@@ -94,10 +69,10 @@
       (define before (cell-can-be top))
       (define after
         (for/fold ([before before])
-            ([c (in-list cs)])
+                  ([c (in-list cs)])
           (if (same-x? top c)
-            (set-subtract before (cell-can-be c))
-            before)))
+              (set-subtract before (cell-can-be c))
+              before)))
       (when (= (set-count after) 1)
         (return #t
                 (struct-copy cell top
@@ -153,8 +128,8 @@
        (define-values (changed? ntop nmore)
          (f top (append tried more)))
        (if changed?
-         (values #t (cons ntop nmore))
-         (loop (cons top tried) more))])))
+           (values #t (cons ntop nmore))
+           (loop (cons top tried) more))])))
 
 (define (propagate g)
   (find-pivot propagate-one g))
@@ -162,12 +137,12 @@
 (define (until-fixed-point f o bad? end-f)
   (define-values (changed? no) (f o))
   (if changed?
-    (cons
-     no
-     (if (bad? no)
-       (end-f no)
-       (until-fixed-point f no bad? end-f)))
-    (end-f o)))
+      (cons
+       no
+       (if (bad? no)
+           (end-f no)
+           (until-fixed-point f no bad? end-f)))
+      (end-f o)))
 
 (define (solved? g)
   (andmap (λ (c) (= (set-count (cell-can-be c)) 1)) g))
@@ -178,10 +153,10 @@
 ;; solve-it : grid -> (listof grid)
 (define (solve-it g)
   (let solve-loop
-      ([g g]
-       [backtrack!
-        (λ (i)
-          (error 'solve-it "Failed!"))])
+    ([g g]
+     [backtrack!
+      (λ (i)
+        (error 'solve-it "Failed!"))])
     (define (done? g)
       (cond
         [(solved? g)
@@ -236,14 +211,14 @@
   (define (draw-can-be can-be)
     (define (figi i)
       (if (set-member? can-be i)
-        (fig (number->string i))
-        (fig " ")))
+          (fig (number->string i))
+          (fig " ")))
     (place-image/align
      (if (= 1 (set-count can-be))
-       (scale 3 (fig (number->string (set-first can-be))))
-       (above (beside (figi 1) (figi 2) (figi 3))
-              (beside (figi 4) (figi 5) (figi 6))
-              (beside (figi 7) (figi 8) (figi 9))))
+         (scale 3 (fig (number->string (set-first can-be))))
+         (above (beside (figi 1) (figi 2) (figi 3))
+                (beside (figi 4) (figi 5) (figi 6))
+                (beside (figi 7) (figi 8) (figi 9))))
      0 0
      "left" "top"
      (rectangle CELL-W CELL-H
@@ -254,7 +229,7 @@
     (for/fold ([i
                 (empty-scene (* CELL-W 11)
                              (* CELL-H 11))])
-        ([c (in-list g)])
+              ([c (in-list g)])
       (match-define (cell x y can-be) c)
       (place-image/align
        (draw-can-be can-be)
@@ -269,60 +244,58 @@
        "left" "top"
        i)))
   (big-bang (draw-state 0 empty gs)
-            (on-tick move-right 1/8)
-            (on-draw draw-draw-state)))
+    (on-tick move-right 1/8)
+    (on-draw draw-draw-state)))
 
 ;; Wikipedia Example
-  (define b1
-    (board
-     "53 | 7 |   "
-     "6  |195|   "
-     " 98|   | 6 "
-     "-----------"
-     "8  | 6 |  3"
-     "4  |8 3|  1"
-     "7  | 2 |  6"
-     "-----------"
-     " 6 |   |28 "
-     "   |419|  5"
-     "   | 8 | 79"))
+(define b1
+  (board
+   "53 | 7 |   "
+   "6  |195|   "
+   " 98|   | 6 "
+   "-----------"
+   "8  | 6 |  3"
+   "4  |8 3|  1"
+   "7  | 2 |  6"
+   "-----------"
+   " 6 |   |28 "
+   "   |419|  5"
+   "   | 8 | 79"))
 
-  ;; "Hard" example
-  (define b2
-    (board
-     " 7 | 2 |  5"
-     "  9| 87|  3"
-     " 6 |   | 4 "
-     "-----------"
-     "   | 6 | 17"
-     "9 4|   |8 6"
-     "71 | 5 |   "
-     "-----------"
-     " 9 |   | 8 "
-     "5  |21 |4  "
-     "4  | 9 | 6 "))
+;; "Hard" example
+(define b2
+  (board
+   " 7 | 2 |  5"
+   "  9| 87|  3"
+   " 6 |   | 4 "
+   "-----------"
+   "   | 6 | 17"
+   "9 4|   |8 6"
+   "71 | 5 |   "
+   "-----------"
+   " 9 |   | 8 "
+   "5  |21 |4  "
+   "4  | 9 | 6 "))
 
-  ;; "Evil" example
-  (define b3
-    (board
-     "  8|   | 45"
-     "   | 8 |9  "
-     "  2|4  |   "
-     "-----------"
-     "5  |  1|76 "
-     " 1 | 7 | 8 "
-     " 79|5  |  1"
-     "-----------"
-     "   |  7|4  "
-     "  7| 6 |   "
-     "65 |   |3  "))
+;; "Evil" example
+(define b3
+  (board
+   "  8|   | 45"
+   "   | 8 |9  "
+   "  2|4  |   "
+   "-----------"
+   "5  |  1|76 "
+   " 1 | 7 | 8 "
+   " 79|5  |  1"
+   "-----------"
+   "   |  7|4  "
+   "  7| 6 |   "
+   "65 |   |3  "))
 
-  #;(draw-state-i
+#;(draw-state-i
    (draw-it!
     (solve-it
      b2)))
-
-
 (require sugar/debug)
 (time-avg 10 (void (solve-it b1)))
 (time-avg 10 (void (solve-it b2)))