Drastic Simplification of MPFunction subclass implementations

MathPad/MPFunction.h

@@ -11,12 +11,19 @@
 #import "MPParseError.h"
 #import "MPTerm.h"
 
+#define MPFunctionAccessorImplementation(Accessor, variableName) \
+- (void)set##Accessor:(MPExpression *)value \
+{ \
+    variableName.parent = nil; \
+    variableName = value; \
+    variableName.parent = self; \
+    [self didChangeChildAtIndex:[self indexOfChild:variableName]]; \
+}
+
 @class MPFunction, MPExpression, MPRangePath;
 
 @interface MPFunction : NSObject <NSCoding, NSCopying, MPExpressionElement>
 
-+ (NSString *)localizedFunctionName; // Override
-
 #pragma mark Creation Methods
 
 - (instancetype)init;
@@ -29,13 +36,14 @@
 - (MPExpression *)rootExpression;
 - (NSIndexPath *)indexPath;
 
-- (NSUInteger)numberOfChildren; // Override
-- (MPExpression *)childAtIndex:(NSUInteger)index; // Override
-- (void)setChild:(MPExpression *)child
-         atIndex:(NSUInteger)index; // Override
+- (NSArray *)childrenAccessors; // Override
 
-// May be overridden for performance improvements
-- (NSArray *)children; // Indexes must equal the ones from the native methods
+- (NSUInteger)numberOfChildren;
+- (MPExpression *)childAtIndex:(NSUInteger)index;
+- (void)setChild:(MPExpression *)child
+         atIndex:(NSUInteger)index;
+
+- (NSArray *)children; // Indexes must equal the ones from the other methods
 - (NSUInteger)indexOfChild:(MPExpression *)child;
 
 - (id)elementAtIndexPath:(NSIndexPath *)indexPath;
@@ -47,15 +55,14 @@
 #pragma mark Messages
 - (void)didChangeElementsInRangePath:(MPRangePath *)rangePath
                    replacementLength:(NSUInteger)replacementLength;
-- (void)didChangeChild:(MPExpression *)child;
 - (void)didChangeChildAtIndex:(NSUInteger)index;
 
 #pragma mark Working With Functions
 // - (BOOL)isEqualToFunction:(MPFunction *)aFunction; // Override
 
 - (NSString *)description; // Should be overridden
-- (NSUInteger)hash;// Override
+- (NSUInteger)hash;
 
-- (id)copyWithZone:(NSZone *)zone; // Override
+- (id)copyWithZone:(NSZone *)zone;
 
 @end