Internal Redesign:

- Combined MPExpression and MPMutableExpression
- Abstracted children of MPExpression into MPExpressionElement protocol
- Abstracted most of MPExpressionLayout and MPFunctionLayout into common superclass MPLayout

MathPad/MPFunction.m

@@ -10,12 +10,11 @@
 #import "MPExpression.h"
 #import "MPRangePath.h"
 
-#import "NSIndexPath+MPReverseIndexPath.h"
+#import "NSIndexPath+MPAdditions.h"
 
 @implementation MPFunction
 
 #pragma mark Creation Methods
-
 - (instancetype)init
 {
     self = [super init];
@@ -25,7 +24,6 @@
 }
 
 #pragma mark Working With the Expression Tree
-
 - (NSUInteger)numberOfChildren
 {
     return 0;
@@ -38,63 +36,10 @@
 
 - (void)setChild:(MPExpression *)child
          atIndex:(NSUInteger)index
-{}
-
-#pragma mark Evaluating Functions
-
-- (double)doubleValue
 {
-    return 0;
+    [self didChangeChildAtIndex:index];
 }
 
-#pragma mark Working With Functions
-
-- (BOOL)isEqual:(id)object
-{
-    if (self == object) {
-        return YES;
-    }
-    if (object == nil) {
-        return NO;
-    }
-    if (![object isKindOfClass:[MPFunction class]]) {
-        return NO;
-    }
-    return [self isEqualToFunction:(MPFunction *)object];
-}
-
-- (BOOL)isEqualToFunction:(MPFunction *)aFunction
-{
-    return [aFunction isMemberOfClass:[MPFunction class]] && [self isMemberOfClass:[MPFunction class]];
-}
-
-#pragma mark - NSCopying
-
-- (id)copyWithZone:(NSZone *)zone
-{
-    return [[MPFunction allocWithZone:zone] init];
-}
-
-#pragma mark - NSCoding
-
-- (id)initWithCoder:(NSCoder *)aDecoder
-{
-    self = [super init];
-    if (self) {
-        
-    }
-    return self;
-}
-
-- (void)encodeWithCoder:(NSCoder *)aCoder
-{}
-
-@end
-
-@implementation MPFunction (MPFunctionExtensionMethods)
-
-#pragma mark Working With the Expression Tree
-
 - (NSArray *)children
 {
     NSUInteger childCount = [self numberOfChildren];
@@ -116,16 +61,115 @@
     return NSNotFound;
 }
 
-- (id)symbolAtIndexPath:(NSIndexPath *)indexPath
+- (id)elementAtIndexPath:(NSIndexPath *)indexPath
 {
     if (indexPath.length == 0) {
         return self;
     }
     MPExpression *child = [self childAtIndex:[indexPath indexAtPosition:0]];
-    return [child symbolAtIndexPath:[indexPath indexPathByRemovingFirstIndex]];
+    return [child elementAtIndexPath:[indexPath indexPathByRemovingFirstIndex]];
 }
 
 #pragma mark Evaluating Functions
+- (double)doubleValue
+{
+    return 0;
+}
+
+#pragma mark Notifications
+- (void)didChangeElementsInRangePath:(MPRangePath *)rangePath
+                   replacementLength:(NSUInteger)replacementLength
+{
+    NSUInteger selfIndex = [self.parent indexOfElement:self];
+    MPRangePath *newPath = rangePath.copy;
+    newPath.location = [newPath.location indexPathByPreceedingIndex:selfIndex];
+    [self.parent didChangeElementsInRangePath:newPath
+                            replacementLength:replacementLength];
+}
+
+- (void)didChangeChild:(MPExpression *)child
+{
+    [self didChangeChildAtIndex:[self indexOfChild:child]];
+}
+
+- (void)didChangeChildAtIndex:(NSUInteger)index
+{
+    MPRangePath *path = [[MPRangePath alloc] initWithRange:NSMakeRange(index, 1)];
+    [self didChangeElementsInRangePath:path
+                     replacementLength:1];
+}
+
+#pragma mark Working With Functions
+- (BOOL)isEqual:(id)object
+{
+    if (self == object) {
+        return YES;
+    }
+    if (object == nil) {
+        return NO;
+    }
+    if (![object isKindOfClass:[MPFunction class]]) {
+        return NO;
+    }
+    return [self isEqualToFunction:(MPFunction *)object];
+}
+
+- (BOOL)isEqualToFunction:(MPFunction *)aFunction
+{
+    return [aFunction isMemberOfClass:[MPFunction class]] && [self isMemberOfClass:[MPFunction class]];
+}
+
+- (NSString *)description
+{
+    return @"[]";
+}
+
+- (NSUInteger)hash
+{
+    return 0;
+}
+
+#pragma mark - NSCopying
+- (id)copyWithZone:(NSZone *)zone
+{
+    return [[MPFunction allocWithZone:zone] init];
+}
+
+#pragma mark - NSCoding
+- (id)initWithCoder:(NSCoder *)aDecoder
+{
+    self = [super init];
+    if (self) {
+        NSArray *children = [aDecoder decodeObject];
+        NSInteger index = 0;
+        for (MPExpression *child in children) {
+            [self setChild:child atIndex:index];
+            ++index;
+        }
+    }
+    return self;
+}
+
+- (void)encodeWithCoder:(NSCoder *)aCoder
+{
+    [aCoder encodeObject:self.children];
+}
+
+#pragma mark - MPExpressionElement
+- (BOOL)isString
+{
+    return NO;
+}
+
+- (BOOL)isFunction
+{
+    return YES;
+}
+
+- (NSUInteger)length
+{
+    return 1;
+}
 
 - (float)floatValue
 {
@@ -147,26 +191,4 @@
     return (long long)[self doubleValue];
 }
 
-- (NSString *)description
-{
-    return @"[]";
-}
-
-- (NSUInteger)hash
-{
-    return 0;
-}
-
 @end
-
-@implementation MPFunction (MPDisplayExtension)
-
-- (void)symbolsChangedInRangePath:(MPRangePath *)rangePath replacementLength:(NSUInteger)length
-{
-    NSUInteger index = [self.parent indexOfSymbol:self];
-    NSIndexPath *newLocation = [rangePath.location indexPathByPrecedingIndex:index];
-    MPRangePath *newRangePath = [[MPRangePath alloc] initWithLocation:newLocation length:rangePath.length];
-    [self.parent symbolsChangedInRangePath:newRangePath replacementLength:length];
-}
-
-@end