diff --git a/pitfall/pitfall/binparser/gif-parse.rkt b/pitfall/pitfall/binparser/gif-parse.rkt
index 09513694..d375eab3 100644
--- a/pitfall/pitfall/binparser/gif-parse.rkt
+++ b/pitfall/pitfall/binparser/gif-parse.rkt
@@ -5,33 +5,23 @@
 
 (define unparse-val (make-parameter #f))
 
-(define identity (λ (x) x))
+(struct binary-problem (msg val) #:transparent)
+
+(define (read-bytes-exact count p)
+  (define bs (read-bytes count p))
+  (unless (and (bytes? bs) (= (bytes-length bs) count))
+    (raise (binary-problem (format "byte string length ~a" count) bs)))
+  bs)
+
 
-(define-macro-cases :atomic
-  [(N COUNT) #'(N COUNT identity)]
-  [(N COUNT PROC) #'(λ ()
-                      (define bs (read-bytes COUNT))
-                      (when (< (bytes-length bs) COUNT)
-                        (error 'not-enough-bytes (format "~a needs ~a" 'N COUNT)))
-                      (PROC bs))])
 
 (define (seq->hash xs) (make-hasheq xs))
 
 (define (seq->list xs) (map cdr xs))
 
-(define-macro-cases :seq
-  [(N SEQ ... (:bidi PROC))
-   #'(λ () (if (unparse-val)
-               (report (PROC (unparse-val)))
-               (PROC (map (λ(f) (f)) (list SEQ ...)))))]
-  [(N SEQ ...) #'(N SEQ ... (:bidi identity))])
 
-(struct elem (name val bidi) #:transparent)
 
-(define-macro-cases define-rule
-  [(N ID WHAT) #'(N ID WHAT (:bidi identity))]
-  [(N ID WHAT (:bidi PROC))
-   #'(define ID (λ () (elem 'ID (WHAT) PROC)))])
+
 
 (define-macro (:bidi X) #'X)
 
@@ -40,19 +30,26 @@
       (report (car (map cdr (hash->list x))))
       (make-hasheq (list x))))
 
-(define (bytes->int bs)
-  (if (= (bytes-length bs) 1)
-      (bytes-ref bs 0)
-      (integer-bytes->integer bs #f #f)))
+(define (bytes->integer len x)
+  (when (< (bytes-length x) len) (raise-argument-error 'bytes->integer "too short" x))
+  (cond
+    [(= len 1) (bytes-ref x 0)]
+    [else (integer-bytes->integer x #f #f)]))
+
+(define (integer->bytes len x)
+  (cond
+    [(= len 1) (bytes x)]
+    [else (integer->integer-bytes x len #f #f)]))
 
 (define (bytes->bitfield bs)
   (for*/list ([b (in-bytes bs)]
               [idx (in-range 8)])
-    (bitwise-bit-set? b idx)))
+             (bitwise-bit-set? b idx)))
 
 (define (bytes->string bs)
   (bytes->string/latin-1 bs))
 
+#|
 (define-rule gif (:seq signature version logical-screen-descriptor (:bidi seq->hash)))
 (define-rule signature (:atomic 3 (:bidi bytes->string)))
 (define-rule version (:atomic 3 (:bidi bytes->string)))
@@ -64,22 +61,85 @@
 (define-rule packed (:atomic 1 (:bidi bytes->bitfield)))
 (define-rule bgcolor-idx (:atomic 1 (:bidi bytes->int)))
 (define-rule aspect (:atomic 1 (:bidi bytes->int)))
+|#
+
+(define (:atomic count #:type [type #f])
+  (λ (x)
+    (define-values (input-proc output-proc)
+      (match type
+        [integer?
+         (values (curry bytes->integer count)
+                 (curry integer->bytes count))]
+        [else (values identity identity)]))
+    (if (input-port? x)
+        (input-proc (read-bytes-exact count x))
+        (let ([result (output-proc x)])
+          (unless (and (bytes? result) (= (bytes-length result) count))
+            (raise (binary-problem (format "byte string length ~a" count) result)))
+          result))))
+
+
+(define (list->hash-with-keys keys vals)
+  (make-hash (map cons keys vals)))
+
+(define (hash->list-with-keys keys h)
+  (for/list ([k (in-list keys)])
+            (hash-ref h k)))
+
+(define (procedure-name proc)
+  (string->symbol (cadr (regexp-match #rx"^#<procedure:(.*?)>$" (with-output-to-string (λ () (display proc)))))))
+
+(define (hash-has-keys? h keys)
+  (define (sortation xs)  (sort xs #:key symbol->string string<?)) 
+  (equal? (sortation (hash-keys h)) (sortation keys)))
+
+(define (:seq #:type [type #f] . rule-procs)
+  (λ (x) (define-values (input-proc output-proc output-check)
+           (cond
+             [(equal? type hash?)
+              (define rule-proc-names (map procedure-name rule-procs))
+              (values (curry list->hash-with-keys rule-proc-names)
+                      (curry hash->list-with-keys rule-proc-names)
+                      (λ (x)
+                        (unless (and (hash? x) (hash-has-keys? x rule-proc-names))
+                          (raise (binary-problem (format "hash with ~a keys, namely ~a" (length rule-procs) rule-proc-names) x)))))]
+             [else (values identity identity
+                           (λ (x)
+                             (unless (and (list? x) (= (length rule-procs) (length x)))
+                               (raise (binary-problem (format "list of ~a values" (length rule-procs)) x)))))]))
+    (match x
+      [(? input-port? p) (input-proc (map (λ (rule-proc) (rule-proc p)) rule-procs))]
+      [else
+       (output-check x)
+       (apply bytes-append (map (λ (rp xi) (rp xi)) rule-procs (output-proc x)))])))
+
+(define-macro-cases :repeat
+  [(_ COUNT RULE-PROC ...) #'(λ (p) (append-map (λ (i) (list (RULE-PROC p) ...)) (range COUNT)))])
 
-(define (make-byte-parser rule)
-  (λ (x) (parse-with-template x rule)))
-
-
-(define (parse-with-template in template)
-  (parameterize ([current-input-port (cond
-                                       [(bytes? in) (open-input-bytes in)]
-                                       [(path-string? in) (open-input-file in)]
-                                       [(input-port? in) in]
-                                       [else (error 'unknown-parse-input-type)])])
-    (template)))
-
-(define (unparse-with-template val template)
-  (parameterize ([unparse-val val])
-    (template)))
+(define-macro-cases define-rule
+  [(_ ID RULE-PROC)
+   (with-pattern ([ID$ (suffix-id #'ID "$")])
+     #'(begin
+         (define (ID [x (current-input-port)])
+           (with-handlers ([binary-problem? (λ (exn)
+                                             (raise-result-error
+                                              'ID
+                                              (binary-problem-msg exn)
+                                              (binary-problem-val exn)))])
+             (RULE-PROC x)))
+         (struct ID$ (val) #:transparent)))])
+
+(define-rule foo (:seq bar zam #:type hash?))
+(define-rule bar (:atomic 1 #:type integer?))
+(define-rule zam (:atomic 2 #:type integer?))
+
+(define-rule foolist (:seq bar zam bar zam))
+
+(check-equal? #"AB" (zam (zam (open-input-bytes #"AB"))) (zam 16961))
+(check-equal?  #"123" (foo (foo (open-input-bytes #"123"))) (foo '#hash((bar . 49) (zam . 13106))))
+
+(foolist (open-input-bytes #"123456"))
+(foolist '(49 13106 52 13877))
 
 (require rackunit)
 #;(check-equal? (parse-with-template "test.gif" gif)
@@ -88,8 +148,4 @@
                                          '(signature . "GIF")
                                          '(version . "87a")))))
 
-#;(define parse-width-bytes (make-byte-parser width))
-(define-rule foo (:atomic 2))
-(define parse-foo-bytes (make-byte-parser foo))
-(define in (open-input-bytes #"12"))
-(parse-foo-bytes in)
+#;(define parse-width-bytes (make-byte-parser width))
\ No newline at end of file