diff --git a/networks.rkt b/networks.rkt
index eedc28c..60ca706 100644
--- a/networks.rkt
+++ b/networks.rkt
@@ -13,18 +13,21 @@
 (require "utils.rkt")
 
 (provide
- ;; Functions with contracts
+ ;; Functions
  (contract-out [update (-> network? state? (listof variable?) state?)]
                [make-state (-> (listof (cons/c symbol? any/c)) state?)]
-               [make-network-from-functions (-> (listof (cons/c symbol? update-function?)) network?)]
-               [update-function-form->update-function (-> update-function-form? update-function?)]
+               [make-network-from-functions (-> (listof (cons/c symbol? update-function/c)) network?)]
+               [update-function-form->update-function (-> update-function-form? update-function/c)]
                [network-form->network (-> network-form? network?)]
                [make-network-from-forms (-> (listof (cons/c symbol? update-function-form?))
                                             network?)])
- ;; Functions
- variable? state? update-function? update-function-form? network-form?
+ ;; Predicates
+ (contract-out [variable? (-> any/c boolean?)]
+               [state? (-> any/c boolean?)]
+               [update-function-form? (-> any/c boolean?)]
+               [network-form? (-> any/c boolean?)])
  ;; Contracts
- state/c network/c
+ state/c network/c update-function/c
  ;; Syntax
  st nn)
 
@@ -42,7 +45,7 @@
 
 ;;; An update function is a function computing a value from the given
 ;;; state.
-(define update-function? (-> state? any/c))
+(define update-function/c (-> state? any/c))
 
 ;;; A network is a mapping from its variables to its update functions.
 (define network? variable-mapping?)