some more errors

csp/csp/hacs.rkt

@@ -101,8 +101,13 @@
   ((csp? name?) ((or/c (listof any/c) procedure?)) . ->* . void?)
   (add-vars! prob (list name) vals-or-procedure))
 
-(define/contract (add-constraints! prob proc namess [proc-name #false])
+(define/contract (add-constraints! prob proc namess [proc-name #false]
+                                   #:caller [caller-id 'add-constraints!])
   ((csp? procedure? (listof (listof name?))) ((or/c #false name?)) . ->* . void?)
+  (unless (procedure? proc)
+    (raise-argument-error caller-id "procedure" proc))
+  (unless (and (list? namess) (andmap (λ (ns) (and (list? ns) (andmap name? ns))) namess))
+    (raise-argument-error caller-id "list of lists of names" namess))
   (set-csp-constraints! prob (append (constraints prob) 
                                      (for/list ([names (in-list namess)])
                                        (for ([name (in-list names)])
@@ -113,15 +118,18 @@
 
 (define/contract (add-pairwise-constraint! prob proc names [proc-name #false])
   ((csp? procedure? (listof name?)) (name?) . ->* . void?)
-  (add-constraints! prob proc (combinations names 2) proc-name))
+  (unless (and (list? names) (andmap name? names))
+    (raise-argument-error 'add-pairwise-constraint! "list of names" names))
+  (add-constraints! prob proc (combinations names 2) proc-name #:caller 'add-pairwise-constraint!))
 
 (define/contract (add-constraint! prob proc names [proc-name #false])
   ((csp? procedure? (listof name?)) (name?) . ->* . void?)
-  (add-constraints! prob proc (list names) proc-name))
+  (add-constraints! prob proc (list names) proc-name #:caller 'add-constraint!))
 
-(define/contract (alldiff= x y)
+(define/contract (alldiff x y)
   (any/c any/c . -> . boolean?)
   (not (= x y)))
+(define alldiff= alldiff)
 
 (struct backtrack (histories) #:transparent)
 (define (backtrack! [names null]) (raise (backtrack names)))

csp/csp/scribblings/csp.scrbl

@@ -254,6 +254,8 @@ void?]
 void?]
 )]{
 Imperatively add a new constraint. The constraint applies the function @racket[_func] to the list of variable names given in @racket[_names]. The return value of @racket[_func] does not need to be a Boolean, but any return value other than @racket[#false] is treated as if it were @racket[#true].
+
+@racket[add-constraints!] is the same, but adds the constraint @racket[_func] to each list of variable names in @racket[_namess] (which is therefore a list of lists of variable names).
 }
 
 @defproc[(add-pairwise-constraint!