First implementation (incomplete) of MPExpression and MPFunction.

Declared custom exceptions in MPException.h

MathPad/MPFunction.m

@@ -0,0 +1,135 @@
+//
+//  MPFunction.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 18.04.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPFunction.h"
+
+@implementation MPFunction
+
+#pragma mark Creation Methods
+
+- (instancetype)init
+{
+    self = [super init];
+    if (self) {
+    }
+    return self;
+}
+
+#pragma mark Children
+
+- (NSUInteger)numberOfChildren
+{
+    return 0;
+}
+
+- (MPExpression *)childAtIndex:(NSUInteger)index
+{
+    return nil;
+}
+
+- (void)setChild:(MPExpression *)child atIndex:(NSUInteger)index
+{}
+
+#pragma mark Evaluating Functions
+
+- (double)doubleValue
+{
+    return 0;
+}
+
+#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 Children
+
+- (NSArray *)children
+{
+    NSUInteger childCount = [self numberOfChildren];
+    NSMutableArray *children = [[NSMutableArray alloc] initWithCapacity:childCount];
+    for (NSInteger i = 0; i < childCount; i++) {
+        [children addObject:[self childAtIndex:i]];
+    }
+    return [children copy];
+}
+
+#pragma mark Evaluating Functions
+
+- (float)floatValue
+{
+    return (float)[self doubleValue];
+}
+
+- (int)intValue
+{
+    return (int)[self doubleValue];
+}
+
+- (NSInteger)integerValue
+{
+    return (NSInteger)[self doubleValue];
+}
+
+- (long long)longLongValue
+{
+    return (long long)[self doubleValue];
+}
+
+- (NSString *)description
+{
+    return @"[]";
+}
+
+- (NSUInteger)hash
+{
+    return 0;
+}
+
+@end