From ccc5775f00206035b782a9bcf724df47a0a1e4be Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonygarnockjones@gmail.com>
Date: Tue, 17 Jun 2014 17:01:22 -0400
Subject: [PATCH] Use matcher-key-set/single and set-first

---
 ethernet.rkt | 17 ++++++++---------
 ip.rkt       | 10 +++++-----
 2 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/ethernet.rkt b/ethernet.rkt
index f036540..c3b6da9 100644
--- a/ethernet.rkt
+++ b/ethernet.rkt
@@ -122,15 +122,14 @@
   (compile-gestalt-projection (ethernet-packet (ethernet-interface interface-name (?!)) ? ? ? ? ?)))
 
 (define (gestalt->hwaddr g interface-name)
-  (define hwaddrs (matcher-key-set (gestalt-project g 0 0 #t (hwaddr-projection interface-name))))
-  (match (set->list hwaddrs)
-    ['() #f]
-    [(list (list h)) h]
-    [(and hs (list* (list h) _))
-     (log-warning "gestalt->hwaddr: multiple addresses for interface ~a: ~v"
-		  interface-name
-		  hs)
-     h]))
+  (define hwaddrs
+    (matcher-key-set/single (gestalt-project g 0 0 #t (hwaddr-projection interface-name))))
+  (case (set-count hwaddrs)
+    [(0) #f]
+    [(1) (set-first hwaddrs)]
+    [else
+     (log-warning "gestalt->hwaddr: multiple addresses for interface ~a: ~v" interface-name hwaddrs)
+     (set-first hwaddrs)]))
 
 (define (ethernet-packet-pattern interface-name from-wire? ethertype)
   (ethernet-packet (ethernet-interface interface-name ?) from-wire? ? ? ethertype ?))
diff --git a/ip.rkt b/ip.rkt
index e0b923f..bd565a5 100644
--- a/ip.rkt
+++ b/ip.rkt
@@ -141,13 +141,13 @@
 	    (match e
 	      [(routing-update g)
 	       (define all-results
-		 (set->list (matcher-key-set (gestalt-project g 0 0 #t arp-result-projection))))
+		 (matcher-key-set/single (gestalt-project g 0 0 #t arp-result-projection)))
 	       (match all-results
 		 [#f (error 'ip "Someone has published a wildcard arp result")]
-		 ['() ;; no results yet, keep waiting
-		  #f]
-		 [(list* (list remote-hwaddr) rest)
-		  (unless (null? rest)
+		 [(? set-empty?) #f] ;; no results yet, keep waiting
+		 [_
+		  (define remote-hwaddr (set-first all-results))
+		  (unless (= 1 (set-count all-results))
 		    (log-warning "Ambiguous arp result for ~a: ~v"
 				 (ip-address->hostname remote-ip)
 				 all-results))