diff --git a/functions.rkt b/functions.rkt
index 5ba88d2..4ab12c2 100644
--- a/functions.rkt
+++ b/functions.rkt
@@ -32,8 +32,8 @@
   [tbf-w (-> tbf? (vectorof number?))]
   [tbf-θ (-> tbf? number?)]
   [vector-boolean->01 (-> (vectorof boolean?) (vectorof (or/c 0 1)))]
-  [apply-tbf (->* (tbf?) #:rest (listof (or/c 0 1)) (or/c 0 1))]
-  [apply-tbf/boolean (->* (tbf?) #:rest (listof boolean?) boolean?)]))
+  [apply-tbf (-> tbf? (vectorof (or/c 0 1)) (or/c 0 1))]
+  [apply-tbf/boolean (-> tbf? (vectorof boolean?) boolean?)]))
 
 (module+ test
   (require rackunit))
@@ -253,11 +253,12 @@
 ;;; Applying a TBF consists in multiplying the weights by the
 ;;; corresponding inputs and comparing the sum of the products to the
 ;;; threshold.
-(define (apply-tbf tbf . inputs)
+(define/contract (apply-tbf tbf inputs)
+  (-> tbf? (vectorof (or/c 0 1)) (or/c 0 1))
   (any->01
    (>
     ;; The scalar product between the inputs and the weights
-    (for/sum ([x (in-list inputs)]
+    (for/sum ([x (in-vector inputs)]
               [w (in-vector (tbf-w tbf))])
       (* x w))
     (tbf-θ tbf))))
@@ -265,15 +266,15 @@
 (module+ test
   (test-case "apply-tbf"
     (define f1 (tbf #(2 -2) 1))
-    (check-equal? (tabulate/01 (λ (x y) (apply-tbf f1 x y)))
+    (check-equal? (tabulate/01 (λ (x y) (apply-tbf f1 (vector x y))))
                   '((0 0 0) (0 1 0) (1 0 1) (1 1 0)))))
 
 ;;; Like apply-tbf, but takes Boolean values as inputs and outputs a
 ;;; boolean value.
-(define (apply-tbf/boolean tbf . inputs)
-  (01->boolean (apply ((curry apply-tbf) tbf) (map any->01 inputs))))
+(define (apply-tbf/boolean tbf inputs)
+  (01->boolean (apply-tbf tbf (vector-map any->01 inputs))))
 
 (module+ test
   (define f1 (tbf #(2 -2) 1))
-  (check-equal? (tabulate/boolean (λ (x y) (apply-tbf/boolean f1 x y)))
+  (check-equal? (tabulate/boolean (λ (x y) (apply-tbf/boolean f1 (vector x y))))
                 '((#f #f #f) (#f #t #f) (#t #f #t) (#t #t #f))))