diff --git a/scheme/lib/dns.scm b/scheme/lib/dns.scm
index 7bbe844..e281933 100644
--- a/scheme/lib/dns.scm
+++ b/scheme/lib/dns.scm
@@ -183,43 +183,44 @@
 (define *on* (ascii->char 1))
 
 ;; message types
-(define types
-  '((unknown 0); types, which are not yet implemented
-    (a 1)      ; a host address 
-    (ns 2)     ; an authoritative name server
-    (md 3)     ; (obsolete)
-    (mf 4)     ; (obsolete)
-    (cname 5)  ; the canonical name for an alias
-    (soa 6)    ; marks the start of a zone of authority
-    (mb 7)     ; (experimental)
-    (mg 8)     ; (experimental)
-    (mr 9)     ; (experimental)
-    (null 10)  ; (experimental)
-    (wks 11)   ; a well known service description
-    (ptr 12)   ; a domain name pointer
-    (hinfo 13) ; host information
-    (minfo 14) ; (experimental)
-    (mx 15)    ; mail exchange
-    (txt 16))) ; text strings
+(define-enumerated-type message-type :message-type
+  message-type?
+  the-message-types
+  message-type-name
+  message-type-index
+  (unknown				; types, which are not yet implemented
+   a					; a host address 
+   ns					; an authoritative name server
+   md					; (obsolete)
+   mf					; (obsolete)
+   cname				; the canonical name for an alias
+   soa					; marks the start of a zone of authority
+   mb					; (experimental)
+   mg					; (experimental)
+   mr					; (experimental)
+   null					; (experimental)
+   wks					; a well known service description
+   ptr					; a domain name pointer
+   hinfo				; host information
+   minfo				; (experimental)
+   mx					; mail exchange
+   txt))				; text strings
 
 ;; message classes
-(define classes
-  '((in 1)     ; the Internet
-    (cs 2)     ; (obsolete)
-    (ch 3)     ; the CHAOS class
-    (hs 4)))   ; Hesoid
+(define-enumerated-type message-class :message-class
+  message-class?
+  the-message-classes
+  message-class-name
+  message-class-index
+  (placeholder ; this starts at 0...
+   in      ; the Internet
+   cs      ; (obsolete)
+   ch      ; the CHAOS class
+   hs))    ; Hesoid
 
 
 ;;; -- useful stuff
 
-;; assoc the other way round
-(define (cossa i l)
-  (cond
-   ((null? l) 'unknown)
-   ((equal? (cadar l) i)
-    (car l))
-   (else (cossa i (cdr l)))))
-
 ;; number: 0<= x < 256
 ;; octet-pair: (char char)
 ;; octet-quad: (char char char char)
@@ -453,14 +454,14 @@
 
 ;; makes a question (name, type, class)
 (define (make-octet-question name type class)
-  (if (not (assoc type types))
-      (dns-error 'invalid-type))
-  (if (not (assoc class classes))
+  (if (not (message-type? type))
+      (dns-error 'invalid-type type))
+  (if (not (message-class? class))
       (dns-error 'invalid-class))
 
   (let* ((qname   (name->octets name))
-	 (qtype   (number->octet-pair (cadr (assoc type types))))
-	 (qclass  (number->octet-pair (cadr (assoc class classes)))))
+	 (qtype   (number->octet-pair (message-type-index type)))
+	 (qclass  (number->octet-pair (message-class-index class))))
     (append qname qtype qclass)))
 
 
@@ -474,8 +475,8 @@
 ;; makes a resource record for ans, nss, ars (name, type, class, ttl, data)
 (define (make-octet-rr name type class ttl rdata)
   (let* ((name (name->octets name))
-	 (type (number->octet-pair (cadr (assoc type types))))
-	 (class (number->octet-pair (cadr (assoc class classes))))
+	 (type (number->octet-pair (message-type-index type)))
+	 (class (number->octet-pair (message-class-index class)))
 	 (ttl (number->octet-quad ttl))
 	 (rdlength (number->octet-pair (length rdata)))
 	 (rdata rdata))
@@ -598,9 +599,9 @@
   (call-with-values
    (lambda () (parse-name start message))
    (lambda (name start)
-     (let ((type (car (cossa (octet-pair->number (car start) (cadr start)) types)))
+     (let ((type (vector-ref the-message-types (octet-pair->number (car start) (cadr start))))
 	   (start (cddr start)))
-       (let ((class (car (cossa (octet-pair->number (car start) (cadr start)) classes)))
+       (let ((class (vector-ref the-message-classes (octet-pair->number (car start) (cadr start))))
 	     (start (cddr start)))
 	 (values (make-question name type class) start))))))
 
@@ -609,9 +610,9 @@
   (call-with-values
    (lambda () (parse-name start message))
    (lambda (name start)
-     (let ((type (car (cossa (octet-pair->number (car start) (cadr start)) types)))
+     (let ((type  (vector-ref the-message-types (octet-pair->number (car start) (cadr start)))) 
 	   (start (cddr start)))
-       (let ((class (car (cossa (octet-pair->number (car start) (cadr start)) classes)))
+       (let ((class (vector-ref the-message-classes (octet-pair->number (car start) (cadr start))))
 	     (start (cddr start)))
 	 (let ((ttl (octet-quad->number (car start) (cadr start)
 					(caddr start) (cadddr start)))
@@ -690,31 +691,31 @@
 
 (define (parse-rr-data type class data message)
   (cond
-   ((eq? type 'a) 
+   ((eq? type (message-type a))
     (make-rr-data-a (octet-ip->address32 data)))
    
-   ((eq? type 'ns) 
+   ((eq? type (message-type ns))
     (make-rr-data-ns (call-with-values 
 		      (lambda () (parse-name data message))
 		      (lambda (name rest) name))))
 
-   ((eq? type 'cname) 
+   ((eq? type (message-type cname))
     (make-rr-data-cname (call-with-values
 			 (lambda () (parse-name data message))
 			 (lambda (name rest) name))))
 
-   ((eq? type 'mx)
+   ((eq? type (message-type mx))
     (make-rr-data-mx (octet-pair->number (car data) (cadr data))
 		     (call-with-values
 		      (lambda ()(parse-name (cddr data) message))
 		      (lambda (name rest) name))))
 
-   ((eq? type 'ptr)
+   ((eq? type (message-type ptr))
     (make-rr-data-ptr (call-with-values
 		       (lambda () (parse-name data message))
 		       (lambda (name rest) name))))
    
-   ((eq? type 'soa)
+   ((eq? type (message-type soa))
     (call-with-values
      (lambda () (parse-name data message))
      (lambda (mname rest)
@@ -733,13 +734,13 @@
 			(rest (cddddr rest)))
 		    (make-rr-data-soa mname rname serial refresh retry expire minimum)))))))))))
 
-   ((eq? type 'hinfo)
+   ((eq? type (message-type hinfo))
     (make-rr-data-hinfo (list->string data)))
 
-   ((eq? type 'txt)
+   ((eq? type (message-type txt))
     (make-rr-data-txt (list->string data)))
    
-   ((eq? type 'wks)
+   ((eq? type (message-type wks))
     (make-rr-data-wks data))
 
    (else (list data))))
@@ -819,7 +820,8 @@
 	  ((2) (dns-error 'dns-server-failure))
 	  ((3) (dns-error 'dns-name-error))
 	  ((4) (dns-error 'dns-not-implemented))
-	  ((5) (dns-error 'dns-refused))))))
+	  ((5) (dns-error 'dns-refused))
+	  (else (error "this must not happend"))))))
 
 ;; #t if message is truncated (could happen via UDP)
 (define (truncated? reply)
@@ -950,7 +952,11 @@
       ((name (question-name (car qds)))
        (type (question-type (car qds)))
        (class (question-class (car qds))))
-    (format #f "~a;~a;~a;~a" nameserver name type class)))
+    (format #f "~a;~a;~a;~a" 
+	    nameserver 
+	    name 
+	    (message-type-name type)
+	    (message-class-name class))))
 
 (define (lookup-cache qds nameserver)
   (let* ((key (make-key qds nameserver))
@@ -1032,7 +1038,7 @@
 		    ;; other nameservers names are found in the nameserver-part,
 		    ;; but their ip-adresses are found in the additonal-rrs
 		    (let ((other-nameservers 
-			   (filter (lambda (elem) (eq? (rr-type elem) 'a))
+			   (filter (lambda (elem) (eq? (rr-type elem) (message-type a)))
 				   (message-additionals (dns-message-reply dns-msg)))))
 		      (lp (if (not (member hit-ns tried)) (cons hit-ns tried) tried)
 			  (lset-union equal?
@@ -1234,8 +1240,8 @@
 			      (ip-string->in-addr-arpa (address32->ip-string name))
 			      (ip-string->in-addr-arpa name)))
 	 (question (if maybe-ip-string	; if name is a ip-addr, the query is a in-addr.arpa address
-		       (make-octet-query-message (random 256) maybe-ip-string type 'in)
-		       (make-octet-query-message (random 256) name type 'in)))
+		       (make-octet-query-message (random 256) maybe-ip-string type (message-class in))
+		       (make-octet-query-message (random 256) name type (message-class in))))
 	 (use-cache? #t)
 	 (protocol 'udp)
 	 (nameservers (check-args nameservers))
@@ -1257,16 +1263,16 @@
 			      (ip-string->in-addr-arpa name)))
 	 (question (if maybe-ip-string	; if name is a ip-addr, the query is a in-addr.arpa address
 		       (dns-error 'not-a-hostname)
-		       (make-octet-query-message (random 256) name 'a 'in)))
+		       (make-octet-query-message (random 256) name (message-type a) (message-class in))))
 	 (use-cache? #t)
 	 (protocol 'udp)
 	 (nameservers (check-args nameservers))
 	 (check-answer (lambda (dns-msg) 
 			 (let* ((reply (dns-message-reply dns-msg))
 				(answers (message-answers reply)))
-			   (not (null? (filter-type answers 'a))))))
+			   (not (null? (filter-type answers (message-type a)))))))
 	 (dns-msg (dns-get-information question use-cache? protocol nameservers check-answer))
-	 (answers (filter-type (message-answers (dns-message-reply dns-msg)) 'a)))
+	 (answers (filter-type (message-answers (dns-message-reply dns-msg)) (message-type a))))
     (rr-data-a-ip (rr-data (car answers)))))
 
 ;; looks up an ip, returns a hostname
@@ -1276,7 +1282,7 @@
 			      (ip-string->in-addr-arpa (address32->ip-string ip))
 			      (ip-string->in-addr-arpa ip)))
 	 (question (if maybe-ip-string	; if name is a ip-addr, the query is a in-addr.arpa address
-		       (make-octet-query-message (random 256) maybe-ip-string 'ptr 'in)
+		       (make-octet-query-message (random 256) maybe-ip-string (message-type ptr) (message-class in))
 		       (dns-error 'not-a-ip)))
 	 (use-cache? #t)
 	 (protocol 'udp)
@@ -1284,9 +1290,9 @@
 	 (check-answer (lambda (dns-msg) 
 			 (let* ((reply (dns-message-reply dns-msg))
 				(answers (message-answers reply)))
-			   (not (null? (filter-type answers 'ptr))))))
+			   (not (null? (filter-type answers (message-type ptr)))))))
 	 (dns-msg (dns-get-information question use-cache? protocol nameservers check-answer))
-	 (answers (filter-type (message-answers (dns-message-reply dns-msg)) 'ptr)))
+	 (answers (filter-type (message-answers (dns-message-reply dns-msg)) (message-type ptr))))
     (rr-data-ptr-name (rr-data (car answers)))))
 
 (define dns-inverse-lookup dns-lookup-ip)
@@ -1300,7 +1306,7 @@
 			      (ip-string->in-addr-arpa name)))
 	 (question (if maybe-ip-string	; if name is a ip-addr, the query is a in-addr.arpa address
 		       (dns-error 'not-a-hostname)
-		       (make-octet-query-message (random 256) name 'ns 'in)))
+		       (make-octet-query-message (random 256) name (message-type ns) (message-class in))))
 	 (use-cache? #t)
 	 (protocol 'udp)
 	 (nameservers (check-args nameservers))
@@ -1308,13 +1314,13 @@
 			 (let* ((reply (dns-message-reply dns-msg))
 				(answers (message-answers reply))
 				(nameservers (message-nameservers reply)))
-			   (or (not (null? (filter-type nameservers 'soa)))
-			       (not (null? (filter-type answers 'ns)))))))
+			   (or (not (null? (filter-type nameservers (message-type soa))))
+			       (not (null? (filter-type answers (message-type ns))))))))
 	 (dns-msg (dns-get-information question use-cache? protocol nameservers check-answer))
 	 (reply (dns-message-reply dns-msg))
-	 (soa (filter-type (message-nameservers reply) 'soa))
-	 (nss (filter-type (message-answers reply) 'ns))
-	 (add (filter-type (message-additionals reply) 'a)))
+	 (soa (filter-type (message-nameservers reply) (message-type soa)))
+	 (nss (filter-type (message-answers reply) (message-type ns)))
+	 (add (filter-type (message-additionals reply) (message-type a))))
     (if (null? nss)
 	(list (dns-lookup-name (rr-data-soa-mname (rr-data (car soa)))))
 	(map (lambda (elem) (rr-data-a-ip (rr-data elem))) add))))
@@ -1330,7 +1336,7 @@
 			(ip-string->in-addr-arpa name)))
 	 (question (if ip-string	; if name is a ip-addr, the query is a in-addr.arpa address
 		       (dns-error 'not-a-hostname)
-		       (make-octet-query-message (random 256) name 'mx 'in)))
+		       (make-octet-query-message (random 256) name (message-type mx) (message-class in))))
 	 (use-cache? #t)
 	 (protocol 'tcp)
 	 (nameservers (check-args nameservers))
@@ -1338,15 +1344,15 @@
 			 (let* ((reply (dns-message-reply dns-msg))
 				(answers (message-answers reply))
 				(nameservers (message-nameservers reply)))
-			   (or (not (null? (filter-type answers 'mx)))
-			       (not (null? (filter-type answers 'cname)))
-			       (not (null? (filter-type answers 'a)))))))
+			   (or (not (null? (filter-type answers (message-type mx))))
+			       (not (null? (filter-type answers (message-type cname))))
+			       (not (null? (filter-type answers (message-type a))))))))
 	 (dns-msg (dns-get-information question use-cache? protocol nameservers check-answer))
 	 (reply (dns-message-reply dns-msg))
-	 (mx (filter-type (message-answers reply) 'mx))
-	 (soa (filter-type (message-nameservers reply) 'soa))
-	 (cname (filter-type (message-answers reply) 'cname))
-	 (a (filter-type (message-answers reply) 'a)))
+	 (mx (filter-type (message-answers reply) (message-type mx)))
+	 (soa (filter-type (message-nameservers reply)(message-type soa)))
+	 (cname (filter-type (message-answers reply) (message-type cname)))
+	 (a (filter-type (message-answers reply) (message-type a))))
 
     (cond
      ((not (null? a)) 
@@ -1421,13 +1427,13 @@
      ((question? dns-msg)
       (begin
 	(d 4 "name " (question-name dns-msg))
-	(d 4 "type " (question-type dns-msg))
-	(d 4 "class" (question-class dns-msg))))
+	(d 4 "type " (message-type-name (question-type dns-msg)))
+	(d 4 "class" (message-class-name (question-class dns-msg)))))
      ((rr? dns-msg)
       (begin
 	(d 4 "name " (rr-name dns-msg))
-	(d 4 "type " (rr-type dns-msg))
-	(d 4 "class" (rr-class dns-msg))
+	(d 4 "type "(message-type-name (rr-type dns-msg)))
+	(d 4 "class" (message-class-name (rr-class dns-msg)))
 	(d 4 "ttl  " (rr-ttl dns-msg))
 	(d 4 "data " "") (show-dns-message (rr-data dns-msg))))
      ((rr-data-a? dns-msg)
@@ -1510,14 +1516,13 @@
 		     (dns-lookup-ip ip-addr))))))
 
 (define (domains-for-search)
-  (let ((resolv.conf (parse-resolv.conf!)))
-    (cond ((assoc 'domain resolv.conf)
-	   => (lambda (pair)
-		(list (cdr pair))))
-	  ((assoc 'search resolv.conf)
-	   => (lambda (pair)
-		(cdr pair)))
-	  (else '()))))
+  (cond ((assoc 'domain (resolv.conf))
+	 => (lambda (pair)
+	      (list (cdr pair))))
+	((assoc 'search (resolv.conf))
+	 => (lambda (pair)
+	      (cdr pair)))
+	(else '())))
 
 (define (host-fqdn name-or-socket-address)
   (if (socket-address? name-or-socket-address)
diff --git a/scheme/packages.scm b/scheme/packages.scm
index 81121a6..061a0b9 100644
--- a/scheme/packages.scm
+++ b/scheme/packages.scm
@@ -466,6 +466,7 @@
 	ascii
 	formats
 	signals
+	finite-types
 	define-record-types
 	random
 	queues