factorized heightmap code into matrix code, and using records now

common.scm

@@ -12,3 +12,29 @@
 (define (char->number c)
   (- (char->integer c) 48)) ; 48 is ASCII's number zero
 
+(define-record-type matrix (fields width height data))
+(define (matrix-get matrix x y)
+  (if (or (< x 0)
+	  (< y 0)
+	  (>= x (matrix-width matrix))
+	  (>= y (matrix-height matrix)))
+    9
+    (vector-ref (vector-ref (matrix-data matrix) y) x)))
+(define (matrix-from-data data)
+  (make-matrix
+    (vector-length (vector-ref data 0))
+    (vector-length data)
+    data))
+
+; parse 0-9 numerical data from file and return a matrix
+(define (load-matrix file)
+  (let y-loop [(heightmap '())]
+    (let x-loop [(line '())]
+      (let [(c (get-char file))]
+	(cond
+	  [(eof-object? c)
+	   (matrix-from-data (reverse-list->vector heightmap))]
+	  [(char-whitespace? c)
+	   (y-loop (cons (reverse-list->vector line) heightmap))]
+	  [(char-numeric? c)
+	   (x-loop (cons (char->number c) line))])))))