Improved Model

Added Keyboard Selection Support
Added Mouse Selection Support
Added Keyboard Editing Support
Corrected Some Bugs
Abstracted the Layout System further
Added Functions Button (test)

MathPad/MPExpression.h

@@ -216,6 +216,32 @@
 - (NSUInteger)indexOfElement:(id<MPExpressionElement>)element;
 
 
+/*!
+    @method     indexOfElementAtSymbolLocation:offset
+    @brief      Calculates the index of the element the specified location points
+                to.
+ 
+    @discussion The @c location is in the length reference frame whereas the
+                returned value is an element index. This method converts from
+                the former to the latter.
+ 
+                If the location exceeds the receiver's bounds a @c
+                NSRangeException will be raised.
+ 
+    @param      location
+                The location of which you want the corresponding element index.
+ 
+    @param      offset
+                An output parameter that gets set to the offst into the symbol
+                whose index is returned. If location for example points to the
+                symbol @c '2' in the string element @c '123' the offset @c would
+                be set to @c 1.
+ 
+    @return     The index of the element the location points to.
+ */
+- (NSUInteger)indexOfElementAtSymbolLocation:(NSUInteger)location offset:(out NSUInteger *)offset;
+
+
 /*!
     @method     replaceSymbolsInRange:withElements:
     @brief      Replaces the elements in the given range with the contents of the
@@ -242,7 +268,6 @@
  */
 - (void)replaceSymbolsInRange:(NSRange)range
                  withElements:(NSArray *)elements;
-// TODO: - (NSUInteger)indexOfElementAtSymbolLocation:(NSUInteger)location;
 
 #warning Evaluating must possibly return error
 - (double)doubleValue; // Evaluates Expression
@@ -304,6 +329,18 @@
 #pragma mark Working With the Expression Tree
 
 
+/*!
+    @method     rootExpression
+    @brief      Returns the root expression from the receiver's expression tree.
+ 
+    @discussion The root expression is the ultimate parent of all expressions and
+                functions in the expression tree.
+ 
+    @return     The root expression from the receiver's expression tree.
+ */
+- (MPExpression *)rootExpression;
+
+
 /*!
     @method     elementAtIndexPath:
     @brief      Returns the element at the specified index path.
@@ -511,6 +548,19 @@
  */
 - (NSArray *)elements;
 
-// TODO: - (NSMutableArray *)mutableElements;
+
+/*!
+    @method     mutableElements
+    @brief      Returns a proxy mutable array object that responds to all methods
+                defined by @c NSMutableArray.
+ 
+    @discussion Mutations on the proxy object also change the receiver. The proxy
+                object does not respond to coding methods. Copying the proxy
+                object will not duplicate it.
+
+    @return     A proxy object that responds to all methods defined by @c
+                NSMutableArray.
+ */
+// - (NSMutableArray *)mutableElements;
 
 @end