math: grid: Add grid-cell-fold and grid-item-fold procedures.

1 files changed, 15 insertions, 1 deletions

diff --git a/chickadee/math/grid.scm b/chickadee/math/grid.scm
index 830f7d6..7b2b6d6 100644
--- a/chickadee/math/grid.scm
+++ b/chickadee/math/grid.scm
@@ -45,7 +45,9 @@
             grid-item-count
             grid-rect-ref
             for-each-cell
-            for-each-item))
+            grid-cell-fold
+            for-each-item
+            grid-item-fold))
 
 
 ;;;
@@ -192,10 +194,22 @@ cell if RECT is #f."
                                       row))
                      (grid-rows grid))))
 
+(define (grid-cell-fold proc init grid)
+  (hash-fold (lambda (y row memo)
+               (hash-fold (lambda (x cell memo)
+                            (proc cell x y memo))
+                          memo
+                          row))
+             init
+             (grid-rows grid)))
+
 (define (for-each-item proc grid)
   "Call PROC for each item in GRID."
   (hash-for-each proc (grid-rects grid)))
 
+(define (grid-item-fold proc init grid)
+  (hash-fold proc init (grid-rects grid)))
+
 (define (grid-add grid item x y width height)
   "Add ITEM to GRID represented by axis-aligned bounding box defined
 by X, Y, WIDTH, HEIGHT."