day 11 part 2

common.scm

@@ -43,6 +43,8 @@
 	     (< y (matrix-height matrix)))
     (vector-set! (vector-ref (matrix-data matrix) y) x value)))
 
+; print matrix line by line to console
+; each line will be displayed as a scheme-vector
 (define (matrix-print matrix)
   (let y-loop [(y 0)]
     (printf "~a~%" (vector-ref (matrix-data matrix) y))
@@ -61,3 +63,37 @@
 	   (y-loop (cons (reverse-list->vector line) heightmap))]
 	  [(char-numeric? c)
 	   (x-loop (cons (char->number c) line))])))))
+
+; matrix visitor
+; calls function with all coordinates of matrix and value at corresponding point
+; value returned by function is set at the visiting coordinate
+(define (visit-matrix! matrix function)
+  (let [(data (matrix-data matrix))
+	(width-1 (- (matrix-width matrix) 1))
+	(height-1 (- (matrix-height matrix) 1))]
+    (let y-loop [(y 0)]
+      (let x-loop [(x 0)]
+	(let [(value (vector-ref (vector-ref data y) x))]
+	  (vector-set! (vector-ref data y) x
+		       (function x y value))
+	  (when (< x width-1)
+	    (x-loop (+ x 1)))))
+      (when (< y height-1)
+	(y-loop (+ y 1))))))
+
+; increase by 1 value at x,y in given matrix
+; return that value too
+(define (matrix-inc! matrix x y)
+  (let [(v (+ 1 (matrix-get matrix x y 0)))]
+    (matrix-set! matrix x y v)
+    v))
+
+; sum all values of matrix
+(define (matrix-sum matrix)
+  (vector-fold
+    (lambda (y sum line)
+      (+ sum
+	 (vector-fold
+	   (lambda (x sum value) (+ sum value))
+	   0 line)))
+    0 (matrix-data matrix)))