Renamed NSIndexPath+MPRemoveFirstIndex Category to NSIndexPath+MPReverseIndexPath

Added MPDisplayExtension Category to MPExpression and MPFunction
Added Methods to Invalidate the Cache to MPExpressionLayout and MPFunctionLayout

MathPad/MPDisplayExtension.m

@@ -0,0 +1,33 @@
+//
+//  MPExpression+MPDisplayExtension.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 23.04.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPDisplayExtension.h"
+
+@implementation MPExpression (MPDisplayExtension)
+
+- (void)subexpressionChangedAtRangePath:(MPRangePath *)rangePath
+{
+    NSUInteger index = [self.parent indexOfChild:self];
+    NSIndexPath *newLocation = [rangePath.location indexPathByPrecedingIndex:index];
+    [self.parent subexpressionChangedAtRangePath:[[MPRangePath alloc] initWithLocation:newLocation
+                                                                                length:rangePath.length]];
+}
+
+@end
+
+@implementation MPFunction (MPDisplayExtension)
+
+- (void)subexpressionChangedAtRangePath:(MPRangePath *)rangePath
+{
+    NSUInteger index = [self.parent indexOfSymbol:self];
+    NSIndexPath *newLocation = [rangePath.location indexPathByPrecedingIndex:index];
+    [self.parent subexpressionChangedAtRangePath:[[MPRangePath alloc] initWithLocation:newLocation
+                                                                                length:rangePath.length]];
+}
+
+@end