diff --git a/bn-tests.rkt b/bn-tests.rkt
index 0238c49..8dec81e 100644
--- a/bn-tests.rkt
+++ b/bn-tests.rkt
@@ -30,4 +30,9 @@
                [new-s (update bn s '(x2 x1))])
           (check-equal? (hash-ref new-s 'x1) #f)
           (check-equal? (hash-ref new-s 'x2) #t)
-          (check-equal? (length (hash-keys new-s)) 2))))))
+          (check-equal? (length (hash-keys new-s)) 2)))
+
+      (test-case "Constructing networks from forms"
+        (let ([s (make-state '((x . #t) (y . #f)))]
+              [f (update-func-form->update-func '(and x y))])
+          (check-equal? (f s) #f))))))
diff --git a/bn.rkt b/bn.rkt
index d318804..9d3fe20 100644
--- a/bn.rkt
+++ b/bn.rkt
@@ -7,8 +7,10 @@
 ;;; are updated according to their corresponding update functions.
 ;;; The variables to be updated at each step are given by the mode.
 
+(require "utils.rkt")
+
 (provide Variable State UpdateFunc Network
-         update make-state make-bn)
+         update make-state make-bn update-func-form->update-func)
 
 
 ;;; =================
@@ -65,3 +67,8 @@
 ;;; forms of their update functions.
 (define-type NetworkForm (HashTable Variable UpdateFuncForm))
 
+;;; Build an update function from an update function form.
+#;(: update-func-form->update-func (-> UpdateFuncForm UpdateFunc))
+(define (update-func-form->update-func form)
+  (lambda ([s : State])
+    (cast (eval-with1 (cast s (HashTable Variable Any)) form) Boolean)))