Added Expression Tree Inspection Methods

Cleaned Code

MathPad/MPExpression.h

@@ -19,6 +19,14 @@ extern NSString *MPDivisionOperator;
 
 - (instancetype)initWithSymbols:(NSArray *)symbols;
 
+#pragma mark Working With the Expression Tree
+
+@property (nonatomic, weak) MPFunction *parent; // Documentation: Do not set, may be nil
+- (void)functionSymbolChanged:(MPFunction *)symbol
+             atLocalIndexPath:(NSIndexPath *)indexPath; // Index path of change in symbol
+
+- (void)fixSymbols;
+
 #pragma mark Primitive Methods
 
 - (NSUInteger)numberOfSymbols;
@@ -81,6 +89,9 @@ extern NSString *MPDivisionOperator;
 - (void)replaceSymbolsInRange:(NSRange)range
                   withSymbols:(NSArray *)symbols;
 
+- (void)beginEditing;
+- (void)endEditing;
+
 @end
 
 @interface MPMutableExpression (MPMutableExpressionExtensionMethods)