utils: Use hash/c instead of hash-pred.

Also remove hash-pred.

utils.rkt

@@ -11,13 +11,10 @@
  ;; Functions
  (contract-out [eval-with (-> variable-mapping? any/c any)]
                [extract-symbols (-> any/c list?)]
-               [variable-mapping? (-> any/c boolean?)]
-               [hash-pred (->* (hash?)
-                               (#:key-pred any/c #:val-pred any/c)
-                               boolean?)]
+               [variable-mapping? contract?]
                [any->string (-> any/c string?)]
                [variable-mapping-stringify (-> variable-mapping? string-variable-mapping?)]
-               [string-variable-mapping? (-> any/c boolean?)])
+               [string-variable-mapping? contract?])
  ;; Syntax
  auto-hash-ref/explicit auto-hash-ref/:)
 
@@ -29,19 +26,8 @@
 ;;; usage of hash tables mapping symbols to values.  The goal is
 ;;; essentially to avoid having to write explicit hash-ref calls.
 
-;;; Checks whether dict is a hash table and whether its keys satisfy
-;;; key-pred and its values satisfy val-pred.  If either of the
-;;; predicates is not supplied, it defaults to true.  For example,
-;;; (hash-pred dict) is equivalent to (hash dict).
-(define/match (hash-pred dict
-                         #:key-pred [key-pred (λ (_) #t)]
-                         #:val-pred [val-pred (λ (_) #t)])
-  [((hash-table (keys vals) ...) key-pred val-pred)
-   (and (andmap key-pred keys) (andmap val-pred vals))]
-  [(_ _ _) #f])
-
 ;;; A variable mapping is a hash table mapping symbols to values.
-(define (variable-mapping? dict) (hash-pred dict #:key-pred symbol?))
+(define (variable-mapping? dict) (hash/c symbol? any/c))
 
 ;;; Given a (HashTable Symbol a) and a sequence of symbols, binds
 ;;; these symbols to the values they are associated to in the hash
@@ -166,7 +152,7 @@
   (with-output-to-string (λ () (display x))))
 
 ;;; A string variable mapping is a mapping from variables to strings.
-(define (string-variable-mapping? dict) (hash-pred dict #:key-pred symbol? #:val-pred string?))
+(define (string-variable-mapping? dict) (hash/c symbol? string?))
 
 ;;; Converts all the values of a variable mapping to string.
 (define (variable-mapping-stringify ht)