diff --git a/iputil.rkt b/iputil.rkt
index 1d6c11d..e2e5748 100644
--- a/iputil.rkt
+++ b/iputil.rkt
@@ -2,7 +2,7 @@
 
 (require racket/struct)
 
-(provide peer subnet
+(provide (struct-out peer) (struct-out subnet)
          string->ip
          ip->string
          string->subnet
@@ -10,45 +10,43 @@
          string->peer)
 
 (struct peer [ip type]
-        #:methods gen:custom-write
-        [(define write-proc
-           (make-constructor-style-printer
-             (lambda (x) 'peer)
-             (lambda (x) (list (ip->string (peer-ip x)) (peer-type x)))))])
+  #:methods gen:custom-write
+  [(define write-proc
+     (make-constructor-style-printer
+      (lambda (x) 'peer)
+      (lambda (x) (list (ip->string (peer-ip x)) (peer-type x)))))])
 
 (struct subnet [ip mask]
-        #:methods gen:custom-write
-        [(define write-proc
-           (make-constructor-style-printer
-             (lambda (x) 'subnet)
-             (lambda (x) (list (subnet->string x)))))])
+  #:methods gen:custom-write
+  [(define write-proc
+     (make-constructor-style-printer
+      (lambda (x) 'subnet)
+      (lambda (x) (list (subnet->string x)))))])
 
 (define (string->ip str)
-  (let ([parts (reverse (string-split str "."))])
-    (for/sum ([i (in-range 4)]
-              [part parts])
-             (arithmetic-shift (string->number part) (* i 8)))))
+  (define parts (reverse (string-split str ".")))
+  (for/sum ([part (in-list parts)]
+            [i (in-naturals)])
+    (arithmetic-shift (string->number part)
+                      (* i 8))))
 
 (define (ip->string ip)
-  (string-join
-    (reverse
-      (for/list ([i (in-range 4)])
-                (number->string (bitwise-and
-                                  (arithmetic-shift ip (* i -8)) 255))))
-      "."))
+  (define parts
+    (reverse (for/list ([i (in-range 4)])
+               (number->string (bitwise-and (arithmetic-shift ip (* i -8))
+                                            255)))))
+  (string-join parts "."))
 
 (define (string->subnet str)
-  (match (string-split str "/")
-         [(list ipstr maskstr) (subnet (string->ip ipstr)
-                                       (string->number maskstr))]))
+  (match-define (list ipstr maskstr) (string-split str "/"))
+  (subnet (string->ip ipstr)
+          (string->number maskstr)))
 
 (define (subnet->string sub)
-  (string-append
-    (ip->string (subnet-ip sub))
-    "/"
-    (number->string (subnet-mask sub))))
+  (format "~a/~a"
+          (subnet-ip sub)
+          (subnet-mask sub)))
 
 (define (string->peer str)
-  (match (string-split str "-")
-         [(list ip type)
-          (peer (string->ip ip) (string->symbol type))]))
+  (match-define (list ip type) (string-split str "-"))
+  (peer (string->ip ip) (string->symbol type)))