Started to Implement Evaluation

Corrected Some Errors
Cleaned Code

MathPad/MPExpressionView.m

@@ -51,7 +51,7 @@
 {
     NSRect expressionBounds = [self.expressionStorage.rootLayout bounds];
     CGFloat y = (self.bounds.size.height - expressionBounds.size.height) / 2 + fabs(expressionBounds.origin.y);
-    return NSMakePoint(self.bounds.origin.x, self.bounds.origin.y + y);
+    return NSMakePoint(0, y);
 }
 
 @end
@@ -124,15 +124,19 @@
 
 - (void)initializeExpressionView
 {
+    // Setup the Expression Storage
     MPExpressionStorage *expressionStorage = [[MPExpressionStorage alloc] initWithElements:@[@"12345", [[MPSumFunction alloc] init], [[MPSumFunction alloc] init]]];
     expressionStorage.expressionView = self;
     _expressionStorage = expressionStorage;
-    NSRect frame = NSMakeRect(10, 10, 500, 500);
-    NSButton *button = [[NSButton alloc] initWithFrame:frame];
+    
+    // Setup the Functions Button
+    NSButton *button = [[NSButton alloc] initWithFrame:NSZeroRect];
     button.buttonType = NSSwitchButton;
     [button setTitle:@"Functions"];
     self.functionsButton = button;
     [self addSubview:self.functionsButton];
+    
+    // Setup Selection
     self.selection = [[MPRangePath alloc] initWithRange:NSMakeRange(0, 0)];
     self.caretBlinkRate = 1.0;
     [self restartCaretTimer];
@@ -202,7 +206,9 @@
 - (void)keyDown:(NSEvent *)theEvent
 {
     NSString *characters = theEvent.characters;
-    if (characters.length == 1 && [characters stringByTrimmingCharactersInSet:[NSCharacterSet decimalDigitCharacterSet]].length == 0) {
+    NSMutableCharacterSet *allowedCharacters = [NSMutableCharacterSet alphanumericCharacterSet];
+    [allowedCharacters addCharactersInString:@"+-*/= "];
+    if (characters.length == 1 && [characters stringByTrimmingCharactersInSet:allowedCharacters].length == 0) {
         MPExpression *targetExpression = [self.expressionStorage elementAtIndexPath:[self.selection.location indexPathByRemovingLastIndex]];
         [targetExpression replaceSymbolsInRange:self.selection.rangeAtLastIndex withElements:@[characters]];
         self.selection = MPMakeRangePath([self.selection.location indexPathByIncrementingLastIndex], 0);
@@ -277,7 +283,8 @@
 
 - (void)moveToEndOfLine:(id)sender
 {
-    
+    MPExpression *targetExpression = [self.expressionStorage elementAtIndexPath:[self.selection.location indexPathByRemovingLastIndex]];
+    self.selection = MPMakeRangePath([self.selection.location indexPathByReplacingLastIndexWithIndex:targetExpression.length], 0);
 }
 
 - (void)moveLeftAndModifySelection:(id)sender
@@ -317,12 +324,12 @@
 
 - (void)moveWordRightAndModifySelection:(id)sender
 {
-    
+#warning Unimplemented Method
 }
 
 - (void)moveWordLeftAndModifySelection:(id)sender
 {
-    
+#warning Unimplemented Method
 }
 
 - (void)selectAll:(id)sender
@@ -361,7 +368,7 @@
     // Draw the background
     [super drawRect:dirtyRect];
     [[NSColor whiteColor] set];
-    NSRectFill(self.bounds);
+    NSRectFill(dirtyRect);
     
     // Calculate the position of the expression (probably also forces layout of the expression the first time)
     NSPoint expressionOrigin = self.expressionOrigin;