Added the MPExpressionTree Classes

MathPad/MPFractionFunction.m

@@ -0,0 +1,36 @@
+//
+//  MPFractionFunction.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 07.10.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPFractionFunction.h"
+
+@implementation MPFractionFunction
+
+MPFunctionAccessorImplementation(NominatorExpression, _nominatorExpression)
+MPFunctionAccessorImplementation(DenominatorExpression, _denominatorExpression)
+
+- (NSArray *)childrenAccessors
+{
+    return @[@"nominatorExpression", @"denominatorExpression"];
+}
+
+- (BOOL)validate:(MPParseError *__autoreleasing *)error
+{
+    return [[self.nominatorExpression parse] validate:error] && [[self.denominatorExpression parse] validate:error];
+}
+
+- (NSDecimalNumber *)evaluate
+{
+    return [[[self.nominatorExpression parse] evaluate] decimalNumberByDividingBy:[[self.denominatorExpression parse] evaluate]];
+}
+
+- (NSString *)description
+{
+    return [NSString stringWithFormat:@"%@ / %@", self.nominatorExpression, self.denominatorExpression];
+}
+
+@end