diff --git a/csp/csp/hacs-smm.rkt b/csp/csp/hacs-smm.rkt
deleted file mode 100644
index 58e9ac67..00000000
--- a/csp/csp/hacs-smm.rkt
+++ /dev/null
@@ -1,47 +0,0 @@
-#lang br
-(require "hacs.rkt")
-
-;  SEND
-;+ MORE
-;------
-; MONEY
-
-(define $vd +var)
-
-(define (word-value . xs)
-  (for/sum ([(x idx) (in-indexed (reverse xs))])
-    (* x (expt 10 idx))))
-
-(define vs '(s e n d m o r y))
-(define vds (for/list ([k vs])
-              ($vd k (range 10))))
-
-(define (not= x y) (not (= x y)))
-
-(define alldiffs
-  (for/list ([pr (in-combinations vs 2)])
-    ($constraint pr not=)))
-
-(define (smm-func s e n d m o r y)
-  (= (+ (word-value s e n d) (word-value m o r e)) (word-value m o n e y)))
-
-(define csp ($csp vds (append
-                           
-                           alldiffs
-                           (list
-                            ($constraint vs smm-func)
-                            ($constraint '(s) positive?)
-                            ($constraint '(m) (λ (x) (= 1 x)))
-                            ($constraint '(d e y) (λ (d e y) (= (modulo (+ d e) 10) y)))
-                            ($constraint '(n d r e y) (λ (n d r e y)
-                                                        (= (modulo (+ (word-value n d) (word-value r e)) 100)
-                                                           (word-value e y))))
-                            ($constraint '(e n d o r y) (λ (e n d o r y)
-                                                          (= (modulo (+ (word-value e n d) (word-value o r e)) 1000) (word-value n e y))))))))
-(parameterize ([current-select-variable mrv]
-               [current-order-values lcv]
-               [current-inference mac])
-  (time (solve csp)))
-(nassigns csp)
-(nchecks csp)
-(reset! csp)
\ No newline at end of file
diff --git a/csp/csp/hacs-test-workbench.rkt b/csp/csp/hacs-test-workbench.rkt
index df69806d..e8a05ca8 100644
--- a/csp/csp/hacs-test-workbench.rkt
+++ b/csp/csp/hacs-test-workbench.rkt
@@ -25,6 +25,7 @@
                    (list qa qb))
   (add-constraint! queens (negate =) (list qa qb)))
 
+(current-multithreaded #t)
 (time-avg 10 (solve queens))
 (parameterize ([current-solver min-conflicts-solver])
-  (time-named (solve queens)))
\ No newline at end of file
+  (time-avg 10 (solve queens)))
\ No newline at end of file
diff --git a/csp/csp/hacs-test.rkt b/csp/csp/hacs-test.rkt
index 4c3511b5..73ff798f 100644
--- a/csp/csp/hacs-test.rkt
+++ b/csp/csp/hacs-test.rkt
@@ -6,72 +6,72 @@
 (current-order-values shuffle)
 (current-random #true)
 
-(check-equal? (first-unassigned-variable ($csp (list ($var 'a (range 3)) ($var 'b (range 3))) null))
-              ($var 'a (range 3)))
-(check-equal? (first-unassigned-variable ($csp (list ($avar 'a (range 3)) ($var 'b (range 3))) null))
-              ($var 'b (range 3)))
-(check-false (first-unassigned-variable ($csp (list ($avar 'a (range 3)) ($avar 'b (range 3))) null)))
+(check-equal? (first-unassigned-variable (csp (list (variable 'a (range 3)) (variable 'b (range 3))) null))
+              (variable 'a (range 3)))
+(check-equal? (first-unassigned-variable (csp (list (avar 'a (range 3)) (variable 'b (range 3))) null))
+              (variable 'b (range 3)))
+(check-false (first-unassigned-variable (csp (list (avar 'a (range 3)) (avar 'b (range 3))) null)))
 
 (check-equal?
  ;; no forward checking when no constraints
- ($csp-vars (forward-check ($csp (list ($avar 'a '(1)) ($var 'b (range 2))) null) 'a))
- (list ($avar 'a '(1)) ($var 'b '(0 1))))
+ (csp-vars (forward-check (csp (list (avar 'a '(1)) (variable 'b (range 2))) null) 'a))
+ (list (avar 'a '(1)) (variable 'b '(0 1))))
 
 (check-equal?
- ($csp-vars (forward-check (forward-check ($csp (list ($avar 'a '(1))  ($avar 'b '(0)) ($var 'c '(0 1 2)))
-                                                (list ($constraint '(a c) (negate =))
-                                                      ($constraint '(b c) (negate =)))) 'a) 'b))
- (list ($avar 'a '(1)) ($avar 'b '(0)) ($cvar 'c '(2) '(b a))))
+ (csp-vars (forward-check (forward-check (csp (list (avar 'a '(1))  (avar 'b '(0)) (variable 'c '(0 1 2)))
+                                                (list (constraint '(a c) (negate =))
+                                                      (constraint '(b c) (negate =)))) 'a) 'b))
+ (list (avar 'a '(1)) (avar 'b '(0)) (cvar 'c '(2) '(b a))))
 
 (check-equal?
  ;; no inconsistency: b≠c not checked when fc is relative to a
- ($csp-vars (forward-check ($csp (list ($avar 'a '(1))  ($var 'b (range 2)) ($var 'c '(0)))
-                                 (list ($constraint '(a b) (negate =))
-                                       ($constraint '(b c) (negate =)))) 'a))
- (list ($avar 'a '(1)) ($cvar 'b '(0) '(a)) ($var 'c '(0))))
+ (csp-vars (forward-check (csp (list (avar 'a '(1))  (variable 'b (range 2)) (variable 'c '(0)))
+                                 (list (constraint '(a b) (negate =))
+                                       (constraint '(b c) (negate =)))) 'a))
+ (list (avar 'a '(1)) (cvar 'b '(0) '(a)) (variable 'c '(0))))
 
 (check-equal?
  ;; no inconsistency: a≠b not checked when fc ignores a, which is already assigned
- ($csp-vars (forward-check ($csp (list ($avar 'a '(1))  ($avar 'b '(1)) ($var 'c (range 2)))
-                                 (list ($constraint '(a b) (negate =))
-                                       ($constraint '(b c) (negate =)))) 'b))
- (list ($avar 'a '(1)) ($avar 'b '(1)) ($cvar 'c '(0) '(b))))
+ (csp-vars (forward-check (csp (list (avar 'a '(1))  (avar 'b '(1)) (variable 'c (range 2)))
+                                 (list (constraint '(a b) (negate =))
+                                       (constraint '(b c) (negate =)))) 'b))
+ (list (avar 'a '(1)) (avar 'b '(1)) (cvar 'c '(0) '(b))))
 
 (check-exn $backtrack?
-           (λ () ($csp-vars (forward-check ($csp (list ($avar 'a '(1))
-                                                       ($var 'b '(1)))
-                                                 (list ($constraint '(a b) (negate =)))) 'a))))
+           (λ () (csp-vars (forward-check (csp (list (avar 'a '(1))
+                                                       (variable 'b '(1)))
+                                                 (list (constraint '(a b) (negate =)))) 'a))))
 
 
-(check-equal? ($csp-vars (forward-check ($csp (list ($var 'a '(0))
-                                                    ($var 'b (range 3)))
-                                              (list ($constraint '(a b) <))) 'a))
-              (list ($var 'a '(0)) ($cvar 'b '(1 2) '(a))))
+(check-equal? (csp-vars (forward-check (csp (list (variable 'a '(0))
+                                                    (variable 'b (range 3)))
+                                              (list (constraint '(a b) <))) 'a))
+              (list (variable 'a '(0)) (cvar 'b '(1 2) '(a))))
 
 (check-equal?
  (parameterize ([current-inference forward-check])
-   (length (solve* ($csp (list ($var 'x (range 3))
-                               ($var 'y (range 3))
-                               ($var 'z (range 3)))
-                         (list ($constraint '(x y) <>)
-                               ($constraint '(x z) <>)
-                               ($constraint '(y z) <>)))))) 6)
+   (length (solve* (csp (list (variable 'x (range 3))
+                               (variable 'y (range 3))
+                               (variable 'z (range 3)))
+                         (list (constraint '(x y) <>)
+                               (constraint '(x z) <>)
+                               (constraint '(y z) <>)))))) 6)
 
 (parameterize ([current-inference forward-check])
   (define vds (for/list ([k '(wa nt nsw q t v sa)])
-                        ($var k '(red green blue))))
+                        (variable k '(red green blue))))
   (define cs (list
-              ($constraint '(wa nt) neq?)
-              ($constraint '(wa sa) neq?)
-              ($constraint '(nt sa) neq?)
-              ($constraint '(nt q) neq?)
-              ($constraint '(q sa) neq?)
-              ($constraint '(q nsw) neq?)
-              ($constraint '(nsw sa) neq?)
-              ($constraint '(nsw v) neq?)
-              ($constraint '(v sa) neq?)))
-  (define csp ($csp vds cs))
-  (check-equal? (length (solve* csp)) 18))
+              (constraint '(wa nt) neq?)
+              (constraint '(wa sa) neq?)
+              (constraint '(nt sa) neq?)
+              (constraint '(nt q) neq?)
+              (constraint '(q sa) neq?)
+              (constraint '(q nsw) neq?)
+              (constraint '(nsw sa) neq?)
+              (constraint '(nsw v) neq?)
+              (constraint '(v sa) neq?)))
+  (define aus (csp vds cs))
+  (check-equal? (length (solve* aus)) 18))
 
 
 (define quarters (make-csp))
diff --git a/csp/csp/hacs.rkt b/csp/csp/hacs.rkt
index 23a2cc84..8d21eccc 100644
--- a/csp/csp/hacs.rkt
+++ b/csp/csp/hacs.rkt
@@ -1,5 +1,5 @@
 #lang debug racket
-(require racket/generator graph sugar/debug)
+(require racket/generator graph)
 (provide (all-defined-out))
 
 (define-syntax when-debug
@@ -16,95 +16,97 @@
                     (if (null? argss)
                         (yield (reverse acc))
                         (for ([arg (in-list (car argss))])
-                          (loop (cdr argss) (cons arg acc))))))))
+                             (loop (cdr argss) (cons arg acc))))))))
 
-(struct $csp (vars 
+(struct csp (vars 
               constraints
               [assignments #:auto]
               [checks #:auto]) #:mutable #:transparent
   #:auto-value 0)
-(define csp? $csp?)
-(define vars $csp-vars)
-(define constraints $csp-constraints)
-(define-syntax-rule (in-constraints csp) (in-list ($csp-constraints csp)))
-(define-syntax-rule (in-vars csp) (in-list ($csp-vars csp)))
-(define-syntax-rule (in-var-names csp) (in-list (map $var-name ($csp-vars csp))))
-
-(struct $constraint (names proc) #:transparent
+(define vars csp-vars)
+(define constraints csp-constraints)
+(define-syntax-rule (in-constraints csp) (in-list (csp-constraints csp)))
+(define-syntax-rule (in-vars csp) (in-list (csp-vars csp)))
+(define-syntax-rule (in-variable-names csp) (in-list (map variable-name (csp-vars csp))))
+
+(struct constraint (names proc) #:transparent
   #:property prop:procedure
-  (λ (constraint csp)
-    (unless ($csp? csp)
-      (raise-argument-error '$constraint-proc "$csp" csp))
+  (λ (const prob)
+    (unless (csp? prob)
+      (raise-argument-error '$constraint-proc "$csp" prob))
     ;; apply proc in many-to-many style
-    (for/and ([args (in-cartesian (map (λ (cname) ($csp-vals csp cname)) ($constraint-names constraint)))])
-      (apply ($constraint-proc constraint) args))))
+    (for/and ([args (in-cartesian (map (λ (name) (csp-domain prob name)) (constraint-names const)))])
+             (apply (constraint-proc const) args))))
 
 (define (make-constraint [names null] [proc values])
-  ($constraint names proc))
+  (constraint names proc))
 
-(define constraint-names $constraint-names)
-(define constraint? $constraint?)
 
-(define (csp->graphviz csp)
-  (define g (csp->graph csp))
+(define (csp->graphviz prob)
+  (define g (csp->graph prob))
   (graphviz g #:colors (coloring/brelaz g)))
 
-(define (csp->graph csp)
-  (for*/fold ([g (unweighted-graph/undirected (map var-name (vars csp)))])
-             ([constraint (in-constraints csp)]
+(define (csp->graph prob)
+  (for*/fold ([gr (unweighted-graph/undirected (map variable-name (vars prob)))])
+             ([constraint (in-constraints prob)]
               [edge (in-combinations (constraint-names constraint) 2)])
-    (apply add-edge! g edge)
-    g))
+    (apply add-edge! gr edge)
+    gr))
 
-(struct $var (name domain) #:transparent)
-(define var? $var?)
+(struct variable (name domain) #:transparent)
 (define name? symbol?)
-(define $var-vals $var-domain)
-(define var-name $var-name)
 
-(struct $cvar $var (past) #:transparent)
-(struct $avar $var () #:transparent)
-(define assigned-var? $avar?)
+(struct checked-var variable (past) #:transparent)
+(define cvar checked-var)
+(define cvar? checked-var?)
+
+(struct assigned-var variable () #:transparent)
+(define avar assigned-var)
+(define avar? assigned-var?)
 
-(define/contract (make-csp [vars null] [constraints null])
-  (() ((listof var?) (listof constraint?)) . ->* . csp?)
-  ($csp vars constraints))
+(define/contract (make-csp [vars null] [consts null])
+  (() ((listof variable?) (listof constraint?)) . ->* . csp?)
+  (csp vars consts))
 
-(define/contract (add-vars! csp names-or-procedure [vals-or-procedure empty])
+(define/contract (add-variables! prob names-or-procedure [vals-or-procedure empty])
   ((csp? (or/c (listof name?) procedure?)) ((or/c (listof any/c) procedure?)) . ->* . void?)
-  (for/fold ([vars ($csp-vars csp)]
-             #:result (set-$csp-vars! csp vars))
+  (for/fold ([vars (csp-vars prob)]
+             #:result (set-csp-vars! prob vars))
             ([name (in-list (if (procedure? names-or-procedure)
                                 (names-or-procedure)
                                 names-or-procedure))])
-    (when (memq name (map var-name vars))
+    (when (memq name (map variable-name vars))
       (raise-argument-error 'add-vars! "var that doesn't already exist" name))
-    (append vars (list ($var name
+    (append vars (list (variable name
                              (if (procedure? vals-or-procedure)
                                  (vals-or-procedure)
                                  vals-or-procedure))))))
 
-(define/contract (add-var! csp name [vals-or-procedure empty])
+(define add-vars! add-variables!)
+
+(define/contract (add-variable! prob name [vals-or-procedure empty])
   ((csp? name?) ((or/c (listof any/c) procedure?)) . ->* . void?)
-  (add-vars! csp (list name) vals-or-procedure))
+  (add-vars! prob (list name) vals-or-procedure))
 
-(define/contract (add-constraints! csp proc namess [proc-name #false])
+(define add-var! add-variable!)
+
+(define/contract (add-constraints! prob proc namess [proc-name #false])
   ((csp? procedure? (listof (listof name?))) ((or/c #false name?)) . ->* . void?)
-  (set-$csp-constraints! csp (append (constraints csp) 
-                                     (for/list ([names (in-list namess)])
-                                       (for ([name (in-list names)])
-                                         (check-name-in-csp! 'add-constraints! csp name))
-                                       (make-constraint names (if proc-name
-                                                                  (procedure-rename proc proc-name)
-                                                                  proc))))))
-
-(define/contract (add-pairwise-constraint! csp proc var-names [proc-name #false])
+  (set-csp-constraints! prob (append (constraints prob) 
+                                      (for/list ([names (in-list namess)])
+                                                (for ([name (in-list names)])
+                                                     (check-name-in-csp! 'add-constraints! prob name))
+                                                (make-constraint names (if proc-name
+                                                                           (procedure-rename proc proc-name)
+                                                                           proc))))))
+
+(define/contract (add-pairwise-constraint! prob proc var-names [proc-name #false])
   ((csp? procedure? (listof name?)) (name?) . ->* . void?)
-  (add-constraints! csp proc (combinations var-names 2) proc-name))
+  (add-constraints! prob proc (combinations var-names 2) proc-name))
 
-(define/contract (add-constraint! csp proc var-names [proc-name #false])
+(define/contract (add-constraint! prob proc names [proc-name #false])
   ((csp? procedure? (listof name?)) (name?) . ->* . void?)
-  (add-constraints! csp proc (list var-names) proc-name))
+  (add-constraints! prob proc (list names) proc-name))
 
 (define/contract (alldiff= x y)
   (any/c any/c . -> . boolean?)
@@ -120,37 +122,38 @@
 (define current-random (make-parameter #t))
 (define current-decompose (make-parameter #t))
 
-(define/contract (check-name-in-csp! caller csp name)
+(define/contract (check-name-in-csp! caller prob name)
   (symbol? csp? name? . -> . void?)
-  (define names (map var-name (vars csp)))
+  (define names (map variable-name (vars prob)))
   (unless (memq name names)
     (raise-argument-error caller (format "one of these existing csp var names: ~v" names) name)))
 
-(define/contract (csp-var csp name)
-  (csp? name? . -> . $var?)
-  (check-name-in-csp! 'csp-var csp name)
-  (for/first ([var (in-vars csp)]
-              #:when (eq? name (var-name var)))
-    var))
+(define/contract (csp-var prob name)
+  (csp? name? . -> . variable?)
+  (check-name-in-csp! 'csp-var prob name)
+  (for/first ([var (in-vars prob)]
+              #:when (eq? name (variable-name var)))
+             var))
 
-(define/contract ($csp-vals csp name)
+(define/contract (csp-domain prob name)
   (csp? name? . -> . (listof any/c))
-  (check-name-in-csp! 'csp-vals csp name)
-  ($var-domain (csp-var csp name)))
+  (check-name-in-csp! 'csp-vals prob name)
+  (variable-domain (csp-var prob name)))
 
 (define order-domain-values values)
 
-(define/contract (assigned-name? csp name)
+(define/contract (assigned-name? prob name)
   (csp? name? . -> . any/c)
-  (for/or ([var (in-vars csp)]
+  (for/or ([var (in-vars prob)]
            #:when (assigned-var? var))
-    (eq? name (var-name var))))
+          (eq? name (variable-name var))))
 
-(define (reduce-function-arity proc pattern)
+(define/contract (reduce-function-arity proc pattern)
+  (procedure? (listof any/c) . -> . procedure?)
   (unless (match (procedure-arity proc)
             [(arity-at-least val) (<= val (length pattern))]
             [(? number? val) (= val (length pattern))])
-    (raise-argument-error 'reduce-arity (format "list of length ~a, same as procedure arity" (procedure-arity proc)) pattern))
+    (raise-argument-error 'reduce-function-arity (format "list of length ~a, same as procedure arity" (procedure-arity proc)) pattern))
   (define reduced-arity-name (string->symbol (format "reduced-arity-~a" (object-name proc))))
   (define-values (boxed-id-names vals) (partition box? pattern))
   (define new-arity (length boxed-id-names))
@@ -168,80 +171,82 @@
                        (values (cons (car vals) acc) xs (cdr vals))))))
    reduced-arity-name))
 
-(define/contract (reduce-constraint-arity csp [minimum-arity 3])
+(define/contract (reduce-constraint-arity prob [minimum-arity 3])
   ((csp?) ((or/c #false exact-nonnegative-integer?)) . ->* . csp?)
-  (let ([assigned-name? (curry assigned-name? csp)])
+  (let ([assigned-name? (curry assigned-name? prob)])
     (define (partially-assigned? constraint)
-      (ormap assigned-name? ($constraint-names constraint)))
-    (make-csp (vars csp)
-              (for/list ([constraint (in-constraints csp)])
-                (cond
-                  [(and (or (not minimum-arity) (<= minimum-arity (constraint-arity constraint)))
-                        (partially-assigned? constraint))
-                   (match-define ($constraint cnames proc) constraint)
-                   ($constraint (filter-not assigned-name? cnames)
-                                ;; pattern is mix of values and boxed symbols (indicating variables to persist)
-                                ;; use boxes here as cheap way to distinguish id symbols from value symbols
-                                (let ([reduce-arity-pattern (for/list ([cname (in-list cnames)])
-                                                              (if (assigned-name? cname)
-                                                                  (first ($csp-vals csp cname))
-                                                                  (box cname)))])
-                                  (reduce-function-arity proc reduce-arity-pattern)))]
-                  [else constraint])))))
+      (ormap assigned-name? (constraint-names constraint)))
+    (make-csp (vars prob)
+              (for/list ([const (in-constraints prob)])
+                        (cond
+                          [(and (or (not minimum-arity) (<= minimum-arity (constraint-arity const)))
+                                (partially-assigned? const))
+                           (match-define (constraint cnames proc) const)
+                           (constraint (filter-not assigned-name? cnames)
+                                        ;; pattern is mix of values and boxed symbols (indicating variables to persist)
+                                        ;; use boxes here as cheap way to distinguish id symbols from value symbols
+                                        (let ([reduce-arity-pattern (for/list ([cname (in-list cnames)])
+                                                                              (if (assigned-name? cname)
+                                                                                  (first (csp-domain prob cname))
+                                                                                  (box cname)))])
+                                          (reduce-function-arity proc reduce-arity-pattern)))]
+                          [else const])))))
 
 (define nassns 0)
+
 (define (reset-assns!) (set! nassns 0))
-(define/contract (assign-val csp name val)
+
+(define/contract (assign-val prob name val)
   (csp? name? any/c . -> . csp?)
   (when-debug (set! nassns (add1 nassns)))
   (make-csp
-   (for/list ([var (vars csp)])
-     (if (eq? name (var-name var))
-         ($avar name (list val))
-         var))
-   (constraints csp)))
+   (for/list ([var (vars prob)])
+             (if (eq? name (variable-name var))
+                 (assigned-var name (list val))
+                 var))
+   (constraints prob)))
 
-(define/contract (unassigned-vars csp)
-  (csp? . -> . (listof (and/c $var? (not/c assigned-var?))))
-  (filter-not assigned-var? (vars csp)))
+(define/contract (unassigned-vars prob)
+  (csp? . -> . (listof (and/c variable? (not/c assigned-var?))))
+  (filter-not assigned-var? (vars prob)))
 
 (define/contract (first-unassigned-variable csp)
-  (csp? . -> . (or/c #false (and/c $var? (not/c assigned-var?))))
+  (csp? . -> . (or/c #false (and/c variable? (not/c assigned-var?))))
   (match (unassigned-vars csp)
     [(? empty?) #false]
     [(cons x _) x]))
 
-(define/contract (minimum-remaining-values csp)
-  (csp? . -> . (or/c #false (and/c $var? (not/c assigned-var?))))
-  (match (unassigned-vars csp)
+(define/contract (minimum-remaining-values prob)
+  (csp? . -> . (or/c #false (and/c variable? (not/c assigned-var?))))
+  (match (unassigned-vars prob)
     [(? empty?) #false]
-    [xs (argmin (λ (var) (length ($var-domain var))) xs)]))
+    [xs (argmin (λ (var) (length (variable-domain var))) xs)]))
 
 (define mrv minimum-remaining-values)
 
-(define/contract (var-degree csp var)
-  (csp? $var? . -> . exact-nonnegative-integer?)
-  (for/sum ([constraint (in-constraints csp)]
-            #:when (memq (var-name var) ($constraint-names constraint)))
-    1))
+(define/contract (var-degree prob var)
+  (csp? variable? . -> . exact-nonnegative-integer?)
+  (for/sum ([const (in-constraints prob)]
+            #:when (memq (variable-name var) (constraint-names const)))
+           1))
 
-(define/contract (blended-variable-selector csp)
-  (csp? . -> . (or/c #false (and/c $var? (not/c assigned-var?))))
-  (define uvars (unassigned-vars csp))
+(define/contract (blended-variable-selector prob)
+  (csp? . -> . (or/c #false (and/c variable? (not/c assigned-var?))))
+  (define uvars (unassigned-vars prob))
   (cond
     [(empty? uvars) #false]
     [(findf singleton-var? uvars)]
-    [else (first (let* ([uvars-by-mrv (sort uvars < #:key (λ (var) (length ($var-domain var))))]
-                        [uvars-by-degree (sort uvars-by-mrv > #:key (λ (var) (var-degree csp var)))])
+    [else (first (let* ([uvars-by-mrv (sort uvars < #:key (λ (var) (length (variable-domain var))))]
+                        [uvars-by-degree (sort uvars-by-mrv > #:key (λ (var) (var-degree prob var)))])
                    uvars-by-degree))]))
 
 (define/contract (remaining-values var)
-  ($var? . -> . exact-nonnegative-integer?)
-  (length ($var-vals var)))
+  (variable? . -> . exact-nonnegative-integer?)
+  (length (variable-domain var)))
 
-(define/contract (mrv-degree-hybrid csp)
-  (csp? . -> . (or/c #f $var?))
-  (define uvars (unassigned-vars csp))
+(define/contract (mrv-degree-hybrid prob)
+  (csp? . -> . (or/c #f variable?))
+  (define uvars (unassigned-vars prob))
   (cond
     [(empty? uvars) #false]
     [else
@@ -251,66 +256,66 @@
        [(list winning-uvar) winning-uvar] 
        [(list mrv-uvars ...)
         ;; use degree as tiebreaker for mrv
-        (define degrees (map (λ (var) (var-degree csp var)) mrv-uvars))
+        (define degrees (map (λ (var) (var-degree prob var)) mrv-uvars))
         (define max-degree (apply max degrees))
         ;; use random tiebreaker for degree
         (random-pick (for/list ([var (in-list mrv-uvars)]
                                 [degree (in-list degrees)]
                                 #:when (= max-degree degree))
-                       var))])]))
+                               var))])]))
   
 (define first-domain-value values)
 
-(define (no-inference csp name) csp)
+(define (no-inference prob name) prob)
 
 (define/contract (relating-only constraints names)
-  ((listof $constraint?) (listof name?) . -> . (listof $constraint?))
-  (for*/list ([constraint (in-list constraints)]
-              [cnames (in-value ($constraint-names constraint))]
+  ((listof constraint?) (listof name?) . -> . (listof constraint?))
+  (for*/list ([const (in-list constraints)]
+              [cnames (in-value (constraint-names const))]
               #:when (and (= (length names) (length cnames))
                           (for/and ([name (in-list names)])
-                            (memq name cnames))))
-    constraint))
+                                   (memq name cnames))))
+             const))
 
-(define (binary-constraint? constraint)
-  (= 2 (constraint-arity constraint)))
+(define (binary-constraint? const)
+  (= 2 (constraint-arity const)))
 
-(define (constraint-relates? constraint name)
-  (memq name ($constraint-names constraint)))
+(define (constraint-relates? const name)
+  (memq name (constraint-names const)))
 
 (define nfchecks 0)
 (define (reset-nfcs!) (set! nfchecks 0))
 
-(define/contract (forward-check csp aname)
+(define/contract (forward-check prob ref-name)
   (csp? name? . -> . csp?)
-  (define aval (first ($csp-vals csp aname)))
+  (define aval (first (csp-domain prob ref-name)))
   (define (check-var var)
     (match var
       ;; don't check against assigned vars, or the reference var
       ;; (which is probably assigned but maybe not)
-      [(? (λ (x) (or (assigned-var? x) (eq? (var-name x) aname)))) var]
-      [($var name vals)
-       (match ((constraints csp) . relating-only . (list aname name))
+      [(? (λ (x) (or (assigned-var? x) (eq? (variable-name x) ref-name)))) var]
+      [(variable name vals)
+       (match ((constraints prob) . relating-only . (list ref-name name))
          [(? empty?) var]
          [constraints
           (define new-vals
             (for/list ([val (in-list vals)]
                        #:when (for/and ([constraint (in-list constraints)])
-                                (let ([proc ($constraint-proc constraint)])
-                                  (if (eq? name (first ($constraint-names constraint)))
-                                      (proc val aval)
-                                      (proc aval val)))))
-              val))
-          ($cvar name new-vals (cons aname (if ($cvar? var)
-                                               ($cvar-past var)
+                                       (let ([proc (constraint-proc constraint)])
+                                         (if (eq? name (first (constraint-names constraint)))
+                                             (proc val aval)
+                                             (proc aval val)))))
+                      val))
+          (checked-var name new-vals (cons ref-name (if (checked-var? var)
+                                               (checked-var-past var)
                                                null)))])]))
-  (define checked-vars (map check-var (vars csp)))
+  (define checked-vars (map check-var (vars prob)))
   (when-debug (set! nfchecks (+ (length checked-vars) nchecks)))
   ;; conflict-set will be empty if there are no empty domains
   (define conflict-set (for*/list ([var (in-list checked-vars)]
-                                   #:when (empty? ($var-domain var))
-                                   [name (in-list ($cvar-past var))])
-                         name))
+                                   #:when (empty? (variable-domain var))
+                                   [name (in-list (checked-var-past var))])
+                                  name))
   ;; for conflict-directed backjumping it's essential to forward-check ALL vars
   ;; (even after an empty domain is generated) and combine their conflicts
   ;; so we can discover the *most recent past var* that could be the culprit.
@@ -321,87 +326,89 @@
   ;; Discard constraints that have produced singleton domains
   ;; (they have no further use)
   (define nonsingleton-constraints
-    (for/list ([constraint (in-constraints csp)]
+    (for/list ([const (in-constraints prob)]
                #:unless (and
-                         (binary-constraint? constraint)
-                         (constraint-relates? constraint aname)
-                         (let ([other-name (first (remq aname ($constraint-names constraint)))])
-                           (singleton-var? (csp-var csp other-name)))))
-      constraint))
+                         (binary-constraint? const)
+                         (constraint-relates? const ref-name)
+                         (let ([other-name (first (remq ref-name (constraint-names const)))])
+                           (singleton-var? (csp-var prob other-name)))))
+              const))
   (make-csp checked-vars nonsingleton-constraints))
 
 (define/contract (constraint-checkable? c names)
-  ($constraint? (listof name?) . -> . any/c)
+  (constraint? (listof name?) . -> . any/c)
   ;; constraint is checkable if all constraint names
   ;; are in target list of names.
-  (for/and ([cname (in-list ($constraint-names c))])
-    (memq cname names)))
+  (for/and ([cname (in-list (constraint-names c))])
+           (memq cname names)))
 
-(define/contract (constraint-arity constraint)
-  ($constraint? . -> . exact-nonnegative-integer?)
-  (length ($constraint-names constraint)))
+(define/contract (constraint-arity const)
+  (constraint? . -> . exact-nonnegative-integer?)
+  (length (constraint-names const)))
 
 (define (singleton-var? var)
-  (= 1 (length ($var-domain var))))
+  (= 1 (length (variable-domain var))))
 
 (define nchecks 0)
 (define (reset-nchecks!) (set! nchecks 0))
-(define/contract (check-constraints csp [mandatory-names #f] #:conflicts [conflict-count? #f])
+(define/contract (check-constraints prob [mandatory-names #f] #:conflicts [conflict-count? #f])
   ((csp?) ((listof name?) #:conflicts boolean?) . ->* . (or/c csp? exact-nonnegative-integer?))
   ;; this time, we're not limited to assigned variables
   ;; (that is, vars that have been deliberately assigned in the backtrack process thus far)
   ;; we also want to use "singleton" vars (that is, vars that have been reduced to a single domain value by forward checking)
-  (define singleton-varnames (for/list ([var (in-vars csp)]
+  (define singleton-varnames (for/list ([var (in-vars prob)]
                                         #:when (singleton-var? var))
-                               (var-name var)))
-  (define-values (checkable-constraints other-constraints)
+                                       (variable-name var)))
+  (define-values (checkable-consts other-consts)
     (partition (λ (c) (and (constraint-checkable? c singleton-varnames)
                            (or (not mandatory-names)
                                (for/and ([name (in-list mandatory-names)])
-                                 (constraint-relates? c name)))))
-               (constraints csp)))
+                                        (constraint-relates? c name)))))
+               (constraints prob)))
   (cond
-    [conflict-count? (define conflict-count
-                       (for/sum ([constraint (in-list checkable-constraints)]
-                                 #:unless (constraint csp))
-                         1))
-                     (when-debug (set! nchecks (+ conflict-count nchecks)))
-                     conflict-count]
-    [else (for ([(constraint idx) (in-indexed (sort checkable-constraints < #:key constraint-arity))]
-                #:unless (constraint csp))
-            (when-debug (set! nchecks (+ (add1 idx) nchecks)))
-            (backtrack!))
-          ;; discard checked constraints, since they have no further reason to live
-          (make-csp (vars csp) other-constraints)]))
-
-(define/contract (make-nodes-consistent csp)
+    [conflict-count?
+     (define conflict-count
+       (for/sum ([constraint (in-list checkable-consts)]
+                 #:unless (constraint prob))
+                1))
+     (when-debug (set! nchecks (+ conflict-count nchecks)))
+     conflict-count]
+    [else
+     (for ([(constraint idx) (in-indexed (sort checkable-consts < #:key constraint-arity))]
+           #:unless (constraint prob))
+          (when-debug (set! nchecks (+ (add1 idx) nchecks)))
+          (backtrack!))
+     ;; discard checked constraints, since they have no further reason to live
+     (make-csp (vars prob) other-consts)]))
+
+(define/contract (make-nodes-consistent prob)
   (csp? . -> . csp?)
   ;; todo: why does this function slow down searches?
   (make-csp
-   (for/list ([var (in-vars csp)])
-     (match-define ($var name vals) var)
-     (define procs (for*/list ([constraint (in-constraints csp)]
-                               [cnames (in-value ($constraint-names constraint))]
-                               #:when (and (= 1 (length cnames)) (eq? name (car cnames))))
-                     ($constraint-proc constraint)))
-     ($var name
-           (for*/fold ([vals vals])
-                      ([proc (in-list procs)])
-             (filter proc vals))))
-   (constraints csp)))
+   (for/list ([var (in-vars prob)])
+             (match-define (variable name vals) var)
+             (define procs (for*/list ([const (in-constraints prob)]
+                                       [cnames (in-value (constraint-names const))]
+                                       #:when (and (= 1 (length cnames)) (eq? name (car cnames))))
+                                      (constraint-proc const)))
+             (variable name
+                   (for*/fold ([vals vals])
+                              ([proc (in-list procs)])
+                     (filter proc vals))))
+   (constraints prob)))
 
 (define/contract (backtracking-solver
-                  csp
+                  prob
                   #:select-variable [select-unassigned-variable
                                      (or (current-select-variable) first-unassigned-variable)]
                   #:order-values [order-domain-values (or (current-order-values) first-domain-value)]
                   #:inference [inference (or (current-inference) no-inference)])
   ((csp?) (#:select-variable procedure? #:order-values procedure? #:inference procedure?) . ->* . generator?)
   (generator ()
-             (let loop ([csp csp])
-               (match (select-unassigned-variable csp)
-                 [#false (yield csp)]
-                 [($var name domain)
+             (let loop ([prob prob])
+               (match (select-unassigned-variable prob)
+                 [#false (yield prob)]
+                 [(variable name domain)
                   (define (wants-backtrack? exn)
                     (and ($backtrack? exn) (or (let ([btns ($backtrack-names exn)])
                                                  (or (empty? btns) (memq name btns))))))
@@ -410,83 +417,91 @@
                             ([val (in-list (order-domain-values domain))])
                     (with-handlers ([wants-backtrack?
                                      (λ (bt) (append conflicts (remq name ($backtrack-names bt))))])
-                      (let* ([csp (assign-val csp name val)]
+                      (let* ([prob (assign-val prob name val)]
                              ;; reduce constraints before inference,
                              ;; to create more forward-checkable (binary) constraints
-                             [csp (reduce-constraint-arity csp)]
-                             [csp (inference csp name)]
-                             [csp (check-constraints csp)])
-                        (loop csp)))
+                             [prob (reduce-constraint-arity prob)]
+                             [prob (inference prob name)]
+                             [prob (check-constraints prob)])
+                        (loop prob)))
                     conflicts)]))))
 
 (define (random-pick xs)
   (list-ref xs (random (length xs))))
 
-(define (assign-random-vals csp)
-  (for/fold ([new-csp csp])
-            ([name (in-var-names csp)])
-    (assign-val new-csp name (random-pick ($csp-vals csp name)))))
+(define (assign-random-vals prob)
+  (for/fold ([new-csp prob])
+            ([name (in-variable-names prob)])
+    (assign-val new-csp name (random-pick (csp-domain prob name)))))
 
-(define (make-min-conflcts-thread csp0 thread-count max-steps [main-thread (current-thread)])
+(define (make-min-conflcts-thread prob-start thread-count max-steps [main-thread (current-thread)])
   (thread
    (λ ()
      (let loop ()
        ;; Generate a complete assignment for all variables (probably with conflicts)
-       (for/fold ([csp (assign-random-vals csp0)])
+       (for/fold ([prob (assign-random-vals prob-start)])
                  ([nth-step (in-range max-steps)])
          ;; Now repeatedly choose a random conflicted variable and change it
-         (match (conflicted-var-names csp)
-           [(? empty?) (thread-send main-thread csp) (loop)]
+         (match (conflicted-variable-names prob)
+           [(? empty?) (thread-send main-thread prob) (loop)]
            [names
             (define name (random-pick names))
-            (define val (min-conflicts-value csp name ($csp-vals csp0 name)))
-            (assign-val csp name val)]))))))
+            (define val (min-conflicts-value prob name (csp-domain prob-start name)))
+            (assign-val prob name val)]))))))
 
-(define/contract (min-conflicts-solver csp [max-steps 100])
-  (($csp?) (integer?) . ->* . generator?)
-  ;; Solve a CSP by stochastic hillclimbing on the number of conflicts.  
+(define/contract (min-conflicts-solver prob [max-steps 100])
+  ((csp?) (integer?) . ->* . generator?)
   (generator ()
              (for ([thread-count 4]) ; todo: what is ideal thread count?
-               (make-min-conflcts-thread csp thread-count max-steps))
+                  (make-min-conflcts-thread prob thread-count max-steps))
              (for ([i (in-naturals)])
-               (yield (thread-receive)))))
-
-(define/contract (conflicted-var-names csp)
-  ($csp? . -> . (listof name?))
+                  (yield (thread-receive)))))
+
+(define/contract (optimal-stop-min proc xs)
+  (procedure? (listof any/c) . -> . any/c)
+  (define-values (sample candidates) (split-at xs (inexact->exact (floor (* .458 (length xs))))))
+  (define threshold (argmin proc sample))
+  (or (for/first ([c (in-list candidates)]
+                  #:when (<= (proc c) threshold))
+                 c)
+      (last candidates)))
+
+(define/contract (conflicted-variable-names prob)
+  (csp? . -> . (listof name?))
   ;; Return a list of variables in current assignment that are conflicted
-  (for/list ([name (in-var-names csp)]
-             #:when (positive? (nconflicts csp name)))
-    name))
+  (for/list ([name (in-variable-names prob)]
+             #:when (positive? (nconflicts prob name)))
+            name))
  
-(define/contract (min-conflicts-value csp name vals)
-  ($csp? name? (listof any/c) . -> . any/c)
+(define/contract (min-conflicts-value prob name vals)
+  (csp? name? (listof any/c) . -> . any/c)
   ;; Return the value that will give var the least number of conflicts
-  (define vals-by-conflict (sort vals < #:key (λ (val) (nconflicts csp name val))
+  (define vals-by-conflict (sort vals < #:key (λ (val) (nconflicts prob name val))
                                  #:cache-keys? #true))
   (for/first ([val (in-list vals-by-conflict)]
-              #:unless (equal? val (first ($csp-vals csp name)))) ;; but change the value
-    val))
+              #:unless (equal? val (first (csp-domain prob name)))) ;; but change the value
+             val))
 
 (define no-value-sig (gensym))
 
-(define/contract (nconflicts csp name [val no-value-sig])
-  (($csp? name?) (any/c) . ->* . exact-nonnegative-integer?)
+(define/contract (nconflicts prob name [val no-value-sig])
+  ((csp? name?) (any/c) . ->* . exact-nonnegative-integer?)
   ;; How many conflicts var: val assignment has with other variables.
   (check-constraints (if (eq? val no-value-sig)
-                         csp
-                         (assign-val csp name val)) (list name) #:conflicts #true))
+                         prob
+                         (assign-val prob name val)) (list name) #:conflicts #true))
 
-(define/contract (csp->assocs csp)
+(define/contract (csp->assocs prob)
   (csp? . -> . (listof (cons/c name? any/c)))
-  (for/list ([var (in-vars csp)])
-    (match var
-      [($var name (list val)) (cons name val)])))
+  (for/list ([var (in-vars prob)])
+            (match var
+              [(variable name (list val)) (cons name val)])))
 
-(define/contract (combine-csps csps)
-  ((listof $csp?) . -> . $csp?)
+(define/contract (combine-csps probs)
+  ((listof csp?) . -> . csp?)
   (make-csp
-   (apply append (map $csp-vars csps))
-   (apply append (map $csp-constraints csps))))
+   (apply append (map csp-vars probs))
+   (apply append (map csp-constraints probs))))
 
 (define/contract (make-cartesian-generator solgens)
   ((listof generator?) . -> . generator?)
@@ -500,18 +515,18 @@
                    (for ([sol (in-stream (car solstreams))])
                         (loop (cdr solstreams) (cons sol sols)))))))
 
-(define/contract (extract-subcsp csp names)
-  ($csp? (listof name?) . -> . $csp?)
+(define/contract (extract-subcsp prob names)
+  (csp? (listof name?) . -> . csp?)
   (make-csp
-   (for/list ([var (in-vars csp)]
-              #:when (memq (var-name var) names))
-     var)
-   (for/list ([constraint (in-constraints csp)]
-              #:when (for/and ([cname (in-list ($constraint-names constraint))])
-                       (memq cname names)))
-     constraint)))
-
-(define/contract (solve* csp
+   (for/list ([var (in-vars prob)]
+              #:when (memq (variable-name var) names))
+             var)
+   (for/list ([const (in-constraints prob)]
+              #:when (for/and ([cname (in-list (constraint-names const))])
+                              (memq cname names)))
+             const)))
+
+(define/contract (solve* prob
                          #:finish-proc [finish-proc csp->assocs]
                          #:solver [solver (or (current-solver) backtracking-solver)]
                          #:limit [max-solutions +inf.0])
@@ -521,21 +536,21 @@
 
   (define subcsps ; decompose into independent csps. `cc` determines "connected components"
     (if (current-decompose)
-        (for/list ([nodeset (in-list (cc (csp->graph csp)))])
-          (extract-subcsp csp nodeset))
-        (list csp)))
+        (for/list ([nodeset (in-list (cc (csp->graph prob)))])
+                  (extract-subcsp prob nodeset))
+        (list prob)))
   
   (for/list ([solution (in-producer (make-cartesian-generator (map solver subcsps)) (void))]
              [idx (in-range max-solutions)])
-    (finish-proc solution)))
+            (finish-proc solution)))
 
-(define/contract (solve csp
+(define/contract (solve prob
                         #:finish-proc [finish-proc csp->assocs]
                         #:solver [solver (or (current-solver) backtracking-solver)]
                         #:limit [max-solutions 1])
   ((csp?) (#:finish-proc procedure? #:solver procedure? #:limit exact-nonnegative-integer?)
           . ->* . (or/c #false any/c))
-  (match (solve* csp #:finish-proc finish-proc #:solver solver #:limit max-solutions)
+  (match (solve* prob #:finish-proc finish-proc #:solver solver #:limit max-solutions)
     [(list solution) solution]
     [(list solutions ...) solutions]
     [else #false]))
diff --git a/csp/csp/info.rkt b/csp/csp/info.rkt
new file mode 100644
index 00000000..9debf269
--- /dev/null
+++ b/csp/csp/info.rkt
@@ -0,0 +1,3 @@
+#lang info
+
+(define scribblings '(("scribblings/csp.scrbl" (multi-page))))
diff --git a/csp/csp/main.rkt b/csp/csp/main.rkt
index f4d54358..334cb23a 100644
--- a/csp/csp/main.rkt
+++ b/csp/csp/main.rkt
@@ -1,4 +1,4 @@
 #lang racket/base
-(require "port/main.rkt")
-(provide (all-from-out "port/main.rkt"))
+(require "hacs.rkt")
+(provide (all-from-out "hacs.rkt"))
 
diff --git a/csp/csp/scribblings/csp.scrbl b/csp/csp/scribblings/csp.scrbl
index 158d5897..6216c9da 100644
--- a/csp/csp/scribblings/csp.scrbl
+++ b/csp/csp/scribblings/csp.scrbl
@@ -5,15 +5,15 @@
 @(define my-eval (make-base-eval))
 @(my-eval `(require csp))
 
-
-@title{csp}
+@title{Constraint-satisfaction problems}
 
 @author[(author+email "Matthew Butterick" "mb@mbtype.com")]
 
-
 @defmodule[csp]
 
-A simple hyphenation engine that uses the Knuth–Liang hyphenation algorithm originally developed for TeX. I have added little to their work. Accordingly, I take little credit.
+@margin-note{This package is in development. I make no commitment to maintaining the public interface documented below.}
+
+A simple solver for constraint-satisfaction problems.
 
 @section{Installation}
 
diff --git a/csp/hacs-test-workbench.rkt b/csp/hacs-test-workbench.rkt
deleted file mode 100644
index e8a05ca8..00000000
--- a/csp/hacs-test-workbench.rkt
+++ /dev/null
@@ -1,31 +0,0 @@
-#lang debug racket
-(require sugar/debug "hacs.rkt")
-
-(current-inference forward-check)
-(current-select-variable mrv)
-(current-order-values shuffle)
-(current-random #true)
-
-;; queens problem
-;; place queens on chessboard so they do not intersect
-
-(define board-size 8)
-
-(define queens (make-csp))
-(define qs (for/list ([q board-size]) (string->symbol (format "q~a" q))))
-(define rows (range (length qs)))
-(add-vars! queens qs rows)
-(define (q-col q) (string->number (string-trim (symbol->string q) "q")))
-(for* ([qs (in-combinations qs 2)])
-  (match-define (list qa qb) qs)
-  (match-define (list qa-col qb-col) (map q-col qs))
-  (add-constraint! queens
-                   (λ (qa-row qb-row)
-                     (not (= (abs (- qa-row qb-row)) (abs (- (q-col qa) (q-col qb)))))) ; same diag?
-                   (list qa qb))
-  (add-constraint! queens (negate =) (list qa qb)))
-
-(current-multithreaded #t)
-(time-avg 10 (solve queens))
-(parameterize ([current-solver min-conflicts-solver])
-  (time-avg 10 (solve queens)))
\ No newline at end of file
diff --git a/csp/hacs.rkt b/csp/hacs.rkt
deleted file mode 100644
index b9b85cbc..00000000
--- a/csp/hacs.rkt
+++ /dev/null
@@ -1,557 +0,0 @@
-#lang debug racket
-(require racket/generator graph sugar/debug)
-(provide (all-defined-out))
-
-(define-syntax when-debug
-  (let ()
-    (define debug #f)
-    (if debug
-        (make-rename-transformer #'begin)
-        (λ (stx) (syntax-case stx ()
-                   [(_ . rest) #'(void)])))))
-
-(define-syntax-rule (in-cartesian x)
-  (in-generator (let ([argss x])
-                  (let loop ([argss argss][acc empty])
-                    (if (null? argss)
-                        (yield (reverse acc))
-                        (for ([arg (in-list (car argss))])
-                          (loop (cdr argss) (cons arg acc))))))))
-
-(struct $csp (vars 
-              constraints
-              [assignments #:auto]
-              [checks #:auto]) #:mutable #:transparent
-  #:auto-value 0)
-(define csp? $csp?)
-(define vars $csp-vars)
-(define constraints $csp-constraints)
-(define-syntax-rule (in-constraints csp) (in-list ($csp-constraints csp)))
-(define-syntax-rule (in-vars csp) (in-list ($csp-vars csp)))
-(define-syntax-rule (in-var-names csp) (in-list (map $var-name ($csp-vars csp))))
-
-(struct $constraint (names proc) #:transparent
-  #:property prop:procedure
-  (λ (constraint csp)
-    (unless ($csp? csp)
-      (raise-argument-error '$constraint-proc "$csp" csp))
-    ;; apply proc in many-to-many style
-    (for/and ([args (in-cartesian (map (λ (cname) ($csp-vals csp cname)) ($constraint-names constraint)))])
-      (apply ($constraint-proc constraint) args))))
-
-(define (make-constraint [names null] [proc values])
-  ($constraint names proc))
-
-(define constraint-names $constraint-names)
-(define constraint? $constraint?)
-
-(define (csp->graphviz csp)
-  (define g (csp->graph csp))
-  (graphviz g #:colors (coloring/brelaz g)))
-
-(define (csp->graph csp)
-  (for*/fold ([g (unweighted-graph/undirected (map var-name (vars csp)))])
-             ([constraint (in-constraints csp)]
-              [edge (in-combinations (constraint-names constraint) 2)])
-    (apply add-edge! g edge)
-    g))
-
-(struct $var (name domain) #:transparent)
-(define var? $var?)
-(define name? symbol?)
-(define $var-vals $var-domain)
-(define var-name $var-name)
-
-(struct $cvar $var (past) #:transparent)
-(struct $avar $var () #:transparent)
-(define assigned-var? $avar?)
-
-(define/contract (make-csp [vars null] [constraints null])
-  (() ((listof var?) (listof constraint?)) . ->* . csp?)
-  ($csp vars constraints))
-
-(define/contract (add-vars! csp names-or-procedure [vals-or-procedure empty])
-  ((csp? (or/c (listof name?) procedure?)) ((or/c (listof any/c) procedure?)) . ->* . void?)
-  (for/fold ([vars ($csp-vars csp)]
-             #:result (set-$csp-vars! csp vars))
-            ([name (in-list (if (procedure? names-or-procedure)
-                                (names-or-procedure)
-                                names-or-procedure))])
-    (when (memq name (map var-name vars))
-      (raise-argument-error 'add-vars! "var that doesn't already exist" name))
-    (append vars (list ($var name
-                             (if (procedure? vals-or-procedure)
-                                 (vals-or-procedure)
-                                 vals-or-procedure))))))
-
-(define/contract (add-var! csp name [vals-or-procedure empty])
-  ((csp? name?) ((or/c (listof any/c) procedure?)) . ->* . void?)
-  (add-vars! csp (list name) vals-or-procedure))
-
-(define/contract (add-constraints! csp proc namess [proc-name #false])
-  ((csp? procedure? (listof (listof name?))) ((or/c #false name?)) . ->* . void?)
-  (set-$csp-constraints! csp (append (constraints csp) 
-                                     (for/list ([names (in-list namess)])
-                                       (for ([name (in-list names)])
-                                         (check-name-in-csp! 'add-constraints! csp name))
-                                       (make-constraint names (if proc-name
-                                                                  (procedure-rename proc proc-name)
-                                                                  proc))))))
-
-(define/contract (add-pairwise-constraint! csp proc var-names [proc-name #false])
-  ((csp? procedure? (listof name?)) (name?) . ->* . void?)
-  (add-constraints! csp proc (combinations var-names 2) proc-name))
-
-(define/contract (add-constraint! csp proc var-names [proc-name #false])
-  ((csp? procedure? (listof name?)) (name?) . ->* . void?)
-  (add-constraints! csp proc (list var-names) proc-name))
-
-(define/contract (alldiff= x y)
-  (any/c any/c . -> . boolean?)
-  (not (= x y)))
-
-(struct $backtrack (names) #:transparent)
-(define (backtrack! [names null]) (raise ($backtrack names)))
-
-(define current-select-variable (make-parameter #f))
-(define current-order-values (make-parameter #f))
-(define current-inference (make-parameter #f))
-(define current-solver (make-parameter #f))
-(define current-random (make-parameter #t))
-(define current-decompose (make-parameter #t))
-(define current-multithreaded (make-parameter #t))
-
-(define/contract (check-name-in-csp! caller csp name)
-  (symbol? csp? name? . -> . void?)
-  (define names (map var-name (vars csp)))
-  (unless (memq name names)
-    (raise-argument-error caller (format "one of these existing csp var names: ~v" names) name)))
-
-(define/contract (csp-var csp name)
-  (csp? name? . -> . $var?)
-  (check-name-in-csp! 'csp-var csp name)
-  (for/first ([var (in-vars csp)]
-              #:when (eq? name (var-name var)))
-    var))
-
-(define/contract ($csp-vals csp name)
-  (csp? name? . -> . (listof any/c))
-  (check-name-in-csp! 'csp-vals csp name)
-  ($var-domain (csp-var csp name)))
-
-(define order-domain-values values)
-
-(define/contract (assigned-name? csp name)
-  (csp? name? . -> . any/c)
-  (for/or ([var (in-vars csp)]
-           #:when (assigned-var? var))
-    (eq? name (var-name var))))
-
-(define (reduce-function-arity proc pattern)
-  (unless (match (procedure-arity proc)
-            [(arity-at-least val) (<= val (length pattern))]
-            [(? number? val) (= val (length pattern))])
-    (raise-argument-error 'reduce-arity (format "list of length ~a, same as procedure arity" (procedure-arity proc)) pattern))
-  (define reduced-arity-name (string->symbol (format "reduced-arity-~a" (object-name proc))))
-  (define-values (boxed-id-names vals) (partition box? pattern))
-  (define new-arity (length boxed-id-names))
-  (procedure-rename
-   (λ xs
-     (unless (= (length xs) new-arity)
-       (apply raise-arity-error reduced-arity-name new-arity xs))
-     (apply proc (for/fold ([acc empty]
-                            [xs xs]
-                            [vals vals]
-                            #:result (reverse acc))
-                           ([pat-item (in-list pattern)])
-                   (if (box? pat-item)
-                       (values (cons (car xs) acc) (cdr xs) vals)
-                       (values (cons (car vals) acc) xs (cdr vals))))))
-   reduced-arity-name))
-
-(define/contract (reduce-constraint-arity csp [minimum-arity 3])
-  ((csp?) ((or/c #false exact-nonnegative-integer?)) . ->* . csp?)
-  (let ([assigned-name? (curry assigned-name? csp)])
-    (define (partially-assigned? constraint)
-      (ormap assigned-name? ($constraint-names constraint)))
-    (make-csp (vars csp)
-              (for/list ([constraint (in-constraints csp)])
-                (cond
-                  [(and (or (not minimum-arity) (<= minimum-arity (constraint-arity constraint)))
-                        (partially-assigned? constraint))
-                   (match-define ($constraint cnames proc) constraint)
-                   ($constraint (filter-not assigned-name? cnames)
-                                ;; pattern is mix of values and boxed symbols (indicating variables to persist)
-                                ;; use boxes here as cheap way to distinguish id symbols from value symbols
-                                (let ([reduce-arity-pattern (for/list ([cname (in-list cnames)])
-                                                              (if (assigned-name? cname)
-                                                                  (first ($csp-vals csp cname))
-                                                                  (box cname)))])
-                                  (reduce-function-arity proc reduce-arity-pattern)))]
-                  [else constraint])))))
-
-(define nassns 0)
-(define (reset-assns!) (set! nassns 0))
-(define/contract (assign-val csp name val)
-  (csp? name? any/c . -> . csp?)
-  (when-debug (set! nassns (add1 nassns)))
-  (make-csp
-   (for/list ([var (vars csp)])
-     (if (eq? name (var-name var))
-         ($avar name (list val))
-         var))
-   (constraints csp)))
-
-(define/contract (unassigned-vars csp)
-  (csp? . -> . (listof (and/c $var? (not/c assigned-var?))))
-  (filter-not assigned-var? (vars csp)))
-
-(define/contract (first-unassigned-variable csp)
-  (csp? . -> . (or/c #false (and/c $var? (not/c assigned-var?))))
-  (match (unassigned-vars csp)
-    [(? empty?) #false]
-    [(cons x _) x]))
-
-(define/contract (minimum-remaining-values csp)
-  (csp? . -> . (or/c #false (and/c $var? (not/c assigned-var?))))
-  (match (unassigned-vars csp)
-    [(? empty?) #false]
-    [xs (argmin (λ (var) (length ($var-domain var))) xs)]))
-
-(define mrv minimum-remaining-values)
-
-(define/contract (var-degree csp var)
-  (csp? $var? . -> . exact-nonnegative-integer?)
-  (for/sum ([constraint (in-constraints csp)]
-            #:when (memq (var-name var) ($constraint-names constraint)))
-    1))
-
-(define/contract (blended-variable-selector csp)
-  (csp? . -> . (or/c #false (and/c $var? (not/c assigned-var?))))
-  (define uvars (unassigned-vars csp))
-  (cond
-    [(empty? uvars) #false]
-    [(findf singleton-var? uvars)]
-    [else (first (let* ([uvars-by-mrv (sort uvars < #:key (λ (var) (length ($var-domain var))))]
-                        [uvars-by-degree (sort uvars-by-mrv > #:key (λ (var) (var-degree csp var)))])
-                   uvars-by-degree))]))
-
-(define/contract (remaining-values var)
-  ($var? . -> . exact-nonnegative-integer?)
-  (length ($var-vals var)))
-
-(define/contract (mrv-degree-hybrid csp)
-  (csp? . -> . (or/c #f $var?))
-  (define uvars (unassigned-vars csp))
-  (cond
-    [(empty? uvars) #false]
-    [else
-     ;; minimum remaining values (MRV) rule
-     (define mrv-arg (argmin remaining-values uvars))
-     (match (filter (λ (var) (= (remaining-values mrv-arg) (remaining-values var))) uvars)
-       [(list winning-uvar) winning-uvar] 
-       [(list mrv-uvars ...)
-        ;; use degree as tiebreaker for mrv
-        (define degrees (map (λ (var) (var-degree csp var)) mrv-uvars))
-        (define max-degree (apply max degrees))
-        ;; use random tiebreaker for degree
-        (random-pick (for/list ([var (in-list mrv-uvars)]
-                                [degree (in-list degrees)]
-                                #:when (= max-degree degree))
-                       var))])]))
-  
-(define first-domain-value values)
-
-(define (no-inference csp name) csp)
-
-(define/contract (relating-only constraints names)
-  ((listof $constraint?) (listof name?) . -> . (listof $constraint?))
-  (for*/list ([constraint (in-list constraints)]
-              [cnames (in-value ($constraint-names constraint))]
-              #:when (and (= (length names) (length cnames))
-                          (for/and ([name (in-list names)])
-                            (memq name cnames))))
-    constraint))
-
-(define (binary-constraint? constraint)
-  (= 2 (constraint-arity constraint)))
-
-(define (constraint-relates? constraint name)
-  (memq name ($constraint-names constraint)))
-
-(define nfchecks 0)
-(define (reset-nfcs!) (set! nfchecks 0))
-
-(define/contract (forward-check csp aname)
-  (csp? name? . -> . csp?)
-  (define aval (first ($csp-vals csp aname)))
-  (define (check-var var)
-    (match var
-      ;; don't check against assigned vars, or the reference var
-      ;; (which is probably assigned but maybe not)
-      [(? (λ (x) (or (assigned-var? x) (eq? (var-name x) aname)))) var]
-      [($var name vals)
-       (match ((constraints csp) . relating-only . (list aname name))
-         [(? empty?) var]
-         [constraints
-          (define new-vals
-            (for/list ([val (in-list vals)]
-                       #:when (for/and ([constraint (in-list constraints)])
-                                (let ([proc ($constraint-proc constraint)])
-                                  (if (eq? name (first ($constraint-names constraint)))
-                                      (proc val aval)
-                                      (proc aval val)))))
-              val))
-          ($cvar name new-vals (cons aname (if ($cvar? var)
-                                               ($cvar-past var)
-                                               null)))])]))
-  (define checked-vars (map check-var (vars csp)))
-  (when-debug (set! nfchecks (+ (length checked-vars) nchecks)))
-  ;; conflict-set will be empty if there are no empty domains
-  (define conflict-set (for*/list ([var (in-list checked-vars)]
-                                   #:when (empty? ($var-domain var))
-                                   [name (in-list ($cvar-past var))])
-                         name))
-  ;; for conflict-directed backjumping it's essential to forward-check ALL vars
-  ;; (even after an empty domain is generated) and combine their conflicts
-  ;; so we can discover the *most recent past var* that could be the culprit.
-  ;; If we just bail out at the first conflict, we may backjump too far based on its history
-  ;; (and thereby miss parts of the search tree)
-  (when (pair? conflict-set)
-    (backtrack! conflict-set))
-  ;; Discard constraints that have produced singleton domains
-  ;; (they have no further use)
-  (define nonsingleton-constraints
-    (for/list ([constraint (in-constraints csp)]
-               #:unless (and
-                         (binary-constraint? constraint)
-                         (constraint-relates? constraint aname)
-                         (let ([other-name (first (remq aname ($constraint-names constraint)))])
-                           (singleton-var? (csp-var csp other-name)))))
-      constraint))
-  (make-csp checked-vars nonsingleton-constraints))
-
-(define/contract (constraint-checkable? c names)
-  ($constraint? (listof name?) . -> . any/c)
-  ;; constraint is checkable if all constraint names
-  ;; are in target list of names.
-  (for/and ([cname (in-list ($constraint-names c))])
-    (memq cname names)))
-
-(define/contract (constraint-arity constraint)
-  ($constraint? . -> . exact-nonnegative-integer?)
-  (length ($constraint-names constraint)))
-
-(define (singleton-var? var)
-  (= 1 (length ($var-domain var))))
-
-(define nchecks 0)
-(define (reset-nchecks!) (set! nchecks 0))
-(define/contract (check-constraints csp [mandatory-names #f] #:conflicts [conflict-count? #f])
-  ((csp?) ((listof name?) #:conflicts boolean?) . ->* . (or/c csp? exact-nonnegative-integer?))
-  ;; this time, we're not limited to assigned variables
-  ;; (that is, vars that have been deliberately assigned in the backtrack process thus far)
-  ;; we also want to use "singleton" vars (that is, vars that have been reduced to a single domain value by forward checking)
-  (define singleton-varnames (for/list ([var (in-vars csp)]
-                                        #:when (singleton-var? var))
-                               (var-name var)))
-  (define-values (checkable-constraints other-constraints)
-    (partition (λ (c) (and (constraint-checkable? c singleton-varnames)
-                           (or (not mandatory-names)
-                               (for/and ([name (in-list mandatory-names)])
-                                 (constraint-relates? c name)))))
-               (constraints csp)))
-  (cond
-    [conflict-count? (define conflict-count
-                       (for/sum ([constraint (in-list checkable-constraints)]
-                                 #:unless (constraint csp))
-                         1))
-                     (when-debug (set! nchecks (+ conflict-count nchecks)))
-                     conflict-count]
-    [else (for ([(constraint idx) (in-indexed (sort checkable-constraints < #:key constraint-arity))]
-                #:unless (constraint csp))
-            (when-debug (set! nchecks (+ (add1 idx) nchecks)))
-            (backtrack!))
-          ;; discard checked constraints, since they have no further reason to live
-          (make-csp (vars csp) other-constraints)]))
-
-(define/contract (make-nodes-consistent csp)
-  (csp? . -> . csp?)
-  ;; todo: why does this function slow down searches?
-  (make-csp
-   (for/list ([var (in-vars csp)])
-     (match-define ($var name vals) var)
-     (define procs (for*/list ([constraint (in-constraints csp)]
-                               [cnames (in-value ($constraint-names constraint))]
-                               #:when (and (= 1 (length cnames)) (eq? name (car cnames))))
-                     ($constraint-proc constraint)))
-     ($var name
-           (for*/fold ([vals vals])
-                      ([proc (in-list procs)])
-             (filter proc vals))))
-   (constraints csp)))
-
-(define/contract (backtracking-solver
-                  csp
-                  #:select-variable [select-unassigned-variable
-                                     (or (current-select-variable) first-unassigned-variable)]
-                  #:order-values [order-domain-values (or (current-order-values) first-domain-value)]
-                  #:inference [inference (or (current-inference) no-inference)])
-  ((csp?) (#:select-variable procedure? #:order-values procedure? #:inference procedure?) . ->* . generator?)
-  (generator ()
-             (let loop ([csp csp])
-               (match (select-unassigned-variable csp)
-                 [#false (yield csp)]
-                 [($var name domain)
-                  (define (wants-backtrack? exn)
-                    (and ($backtrack? exn) (or (let ([btns ($backtrack-names exn)])
-                                                 (or (empty? btns) (memq name btns))))))
-                  (for/fold ([conflicts null]
-                             #:result (void))
-                            ([val (in-list (order-domain-values domain))])
-                    (with-handlers ([wants-backtrack?
-                                     (λ (bt) (append conflicts (remq name ($backtrack-names bt))))])
-                      (let* ([csp (assign-val csp name val)]
-                             ;; reduce constraints before inference,
-                             ;; to create more forward-checkable (binary) constraints
-                             [csp (reduce-constraint-arity csp)]
-                             [csp (inference csp name)]
-                             [csp (check-constraints csp)])
-                        (loop csp)))
-                    conflicts)]))))
-
-(define (random-pick xs)
-  (list-ref xs (random (length xs))))
-
-(define (assign-random-vals csp)
-  (for/fold ([new-csp csp])
-            ([name (in-var-names csp)])
-    (assign-val new-csp name (random-pick ($csp-vals csp name)))))
-
-(define (make-min-conflcts-thread csp0 thread-count max-steps [main-thread (current-thread)])
-  (thread
-   (λ ()
-     (let loop ()
-       ;; Generate a complete assignment for all variables (probably with conflicts)
-       (for/fold ([csp (assign-random-vals csp0)])
-                 ([nth-step (in-range max-steps)])
-         ;; Now repeatedly choose a random conflicted variable and change it
-         (match (conflicted-var-names csp)
-           [(? empty?) (thread-send main-thread csp) (loop)]
-           [names
-            (define name (random-pick names))
-            (define val (min-conflicts-value csp name ($csp-vals csp0 name)))
-            (assign-val csp name val)]))))))
-
-(define/contract (min-conflicts-solver csp [max-steps 100])
-  (($csp?) (integer?) . ->* . generator?)
-  ;; Solve a CSP by stochastic hillclimbing on the number of conflicts.  
-  (generator ()
-             (for ([thread-count (if (current-multithreaded) 4 1)]) ; todo: what is ideal thread count?
-               (make-min-conflcts-thread csp thread-count max-steps))
-             (for ([i (in-naturals)])
-               (yield (thread-receive)))))
-
-(define/contract (conflicted-var-names csp)
-  ($csp? . -> . (listof name?))
-  ;; Return a list of variables in current assignment that are conflicted
-  (for/list ([name (in-var-names csp)]
-             #:when (positive? (nconflicts csp name)))
-    name))
-
-(define/contract (optimal-stop-min proc xs)
-  (procedure? (listof any/c) . -> . any/c)
-  (define-values (sample candidates) (split-at xs (inexact->exact (floor (* .458 (length xs))))))
-  (define threshold (argmin proc sample))
-  (or (for/first ([c (in-list candidates)]
-                  #:when (<= (proc c) threshold))
-        c)
-      (last candidates)))
-  
- 
-(define/contract (min-conflicts-value csp name vals)
-  ($csp? name? (listof any/c) . -> . any/c)
-  ;; Return the value that will give var the least number of conflicts
-  #;(optimal-stop-min (λ (val) (nconflicts csp name val)) vals)
-  (define vals-by-conflict (sort vals < #:key (λ (val) (nconflicts csp name val))
-                                 #:cache-keys? #true))
-  (for/first ([val (in-list vals-by-conflict)]
-              #:unless (equal? val (first ($csp-vals csp name)))) ;; but change the value
-    val))
-
-(define no-value-sig (gensym))
-
-(define/contract (nconflicts csp name [val no-value-sig])
-  (($csp? name?) (any/c) . ->* . exact-nonnegative-integer?)
-  ;; How many conflicts var: val assignment has with other variables.
-  (check-constraints (if (eq? val no-value-sig)
-                         csp
-                         (assign-val csp name val)) (list name) #:conflicts #true))
-
-(define/contract (csp->assocs csp)
-  (csp? . -> . (listof (cons/c name? any/c)))
-  (for/list ([var (in-vars csp)])
-    (match var
-      [($var name (list val)) (cons name val)])))
-
-(define/contract (combine-csps csps)
-  ((listof $csp?) . -> . $csp?)
-  (make-csp
-   (apply append (map $csp-vars csps))
-   (apply append (map $csp-constraints csps))))
-
-(define/contract (make-cartesian-generator solgens)
-  ((listof generator?) . -> . generator?)
-  (generator ()
-             (define solstreams (for/list ([solgen (in-list solgens)])
-                                  (for/stream ([sol (in-producer solgen (void))]) 
-                                    sol))) 
-             (let loop ([solstreams solstreams][sols empty])
-               (if (null? solstreams)
-                   (yield (combine-csps (reverse sols)))
-                   (for ([sol (in-stream (car solstreams))])
-                     (loop (cdr solstreams) (cons sol sols)))))))
-
-(define/contract (extract-subcsp csp names)
-  ($csp? (listof name?) . -> . $csp?)
-  (make-csp
-   (for/list ([var (in-vars csp)]
-              #:when (memq (var-name var) names))
-     var)
-   (for/list ([constraint (in-constraints csp)]
-              #:when (for/and ([cname (in-list ($constraint-names constraint))])
-                       (memq cname names)))
-     constraint)))
-
-(define/contract (solve* csp
-                         #:finish-proc [finish-proc csp->assocs]
-                         #:solver [solver (or (current-solver) backtracking-solver)]
-                         #:limit [max-solutions +inf.0])
-  ((csp?) (#:finish-proc procedure? #:solver procedure? #:limit exact-nonnegative-integer?)
-          . ->* . (listof any/c))
-  (when-debug (reset-assns!) (reset-nfcs!) (reset-nchecks!))          
-
-  (define subcsps ; decompose into independent csps. `cc` determines "connected components"
-    (if (current-decompose)
-        (for/list ([nodeset (in-list (cc (csp->graph csp)))])
-          (extract-subcsp csp nodeset))
-        (list csp)))
-  
-  (for/list ([solution (in-producer (make-cartesian-generator (map solver subcsps)) (void))]
-             [idx (in-range max-solutions)])
-    (finish-proc solution)))
-
-(define/contract (solve csp
-                        #:finish-proc [finish-proc csp->assocs]
-                        #:solver [solver (or (current-solver) backtracking-solver)]
-                        #:limit [max-solutions 1])
-  ((csp?) (#:finish-proc procedure? #:solver procedure? #:limit exact-nonnegative-integer?)
-          . ->* . (or/c #false any/c))
-  (match (solve* csp #:finish-proc finish-proc #:solver solver #:limit max-solutions)
-    [(list solution) solution]
-    [(list solutions ...) solutions]
-    [else #false]))
-
-(define (<> a b) (not (= a b)))
-(define (neq? a b) (not (eq? a b)))
-
diff --git a/csp/info.rkt b/csp/info.rkt
index 5b7681d8..2e2dc245 100644
--- a/csp/info.rkt
+++ b/csp/info.rkt
@@ -1,6 +1,4 @@
 #lang info
 (define collection 'multi)
 (define deps '(("base" #:version "6.0") "sugar" "rackunit-lib" "debug" "graph"))
-(define update-implies '("sugar"))
-(define scribblings '(("csp/scribblings/csp.scrbl" (multi-page))))
-;(define compile-omit-paths '("tests" "raco.rkt"))
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+(define update-implies '("sugar"))
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