From baa670aa8f73f61ce58b54a8406bf33f1381d403 Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Sat, 22 Nov 2014 19:42:25 -0800
Subject: [PATCH] add contract to make-caching-proc

---
 cache.rkt | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/cache.rkt b/cache.rkt
index c44f26b..a698889 100644
--- a/cache.rkt
+++ b/cache.rkt
@@ -1,8 +1,9 @@
 #lang racket/base
-(require (for-syntax racket/base))
+(require (for-syntax racket/base) racket/contract)
 (provide (all-defined-out))
 
-(define (make-caching-proc base-proc) 
+(define/contract (make-caching-proc base-proc) 
+  (procedure? . -> . procedure?)
   (let ([cache (make-hash)])
     (λ args
       (hash-ref! cache args (λ () (apply base-proc args))))))