diff --git a/js/Grid.js b/js/Grid.js
index 69bd1bc..65581ee 100644
--- a/js/Grid.js
+++ b/js/Grid.js
@@ -1,5 +1,6 @@
 import CellSet;
 import * as Dom from UnitJS.Dom;
+import {iter, square} from Grid.Util;
 
 var grid = {
 	element: document.getElementById('grid'),
@@ -8,14 +9,11 @@ var grid = {
 	size: null
 };
 
-var iter = generate; // alias for more intuitive use (discarding the result)
-
 return {
 	cell: cell,
 	clear: clear,
 	init: init,
 	get: get,
-	iter: iter,
 };
 
 function init(size, eventHandlers) {
@@ -37,26 +35,15 @@ function makeRow(config) {
 }
 
 function clear() {
-	grid.data = generate(function() {return; });
+	grid.data = square(grid.size);
 	grid.missing = CellSet.make(
 		{type: 'rectangle', row: 0, column: 0, width: 8, height: 8}
 	);
-	iter(function(row, column) {
+	iter(grid.data, function(row, column) {
 		cell(row, column).className = '';
 	});
 }
 
-function generate(f) {
-	var result = [];
-	for(var row = 0; row < grid.size; row++) {
-		result[row] = [];;
-		for(var column = 0; column < grid.size; column++) {
-			result[row].push(f(row, column));
-		}
-	}
-	return result;
-}
-
 function get() {
 	return grid;
 }
diff --git a/js/Grid/IO.js b/js/Grid/IO.js
index ac74835..9890087 100644
--- a/js/Grid/IO.js
+++ b/js/Grid/IO.js
@@ -2,6 +2,7 @@ import * as File from WTK.File;
 import * as Async from UnitJS.Async;
 import Grid;
 import Grid.Color;
+import iter from Grid.Util;
 import Mode;
 
 return {
@@ -31,7 +32,7 @@ function load() {
 
 function setGridData(data) {
 	if(data != undefined) {
-		Grid.iter(function(row, column) {
+		iter(data, function(row, column) {
 			if(data[row][column] != undefined) {
 				Grid.Color.ize(row, column, data[row][column]);
 			}
diff --git a/js/Grid/Util.js b/js/Grid/Util.js
new file mode 100644
index 0000000..f0f3cb1
--- /dev/null
+++ b/js/Grid/Util.js
@@ -0,0 +1,24 @@
+return {
+	generate: generate,
+	iter: iter,
+	square: square
+};
+
+function generate(width, height, f) {
+	var result = [];
+	for(var row = 0; row < height; row++) {
+		result[row] = [];;
+		for(var column = 0; column < width; column++) {
+			result[row].push(f(row, column));
+		}
+	}
+	return result;
+}
+
+function iter(grid, f) {
+	generate(grid.length > 0 ? grid[0].length : null, grid.length, f);
+}
+
+function square(size) {
+	return generate(size, size, function() {return;});
+}