move common code to common.scm

common.scm

@@ -0,0 +1,9 @@
+; returns a list of numbers parsed from the first line of the file,
+; separated by commas
+(define (read-comma-separated-numbers file)
+  (let loop [(draws '()) (n 0)]
+    (let [(c (get-char file))]
+      (cond
+	[(char=? c #\,) (loop (cons n draws) 0)]
+	[(char-whitespace? c) (reverse (cons n draws))]
+	[else (loop draws (+ (* n 10) (string->number (string c))))]))))