Added the MPExpressionTree Classes

MathPad/MPFunction+MPValue.m

@@ -0,0 +1,28 @@
+//
+//  MPFunction+MPValue.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 09.10.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPFunction+MPValue.h"
+
+@implementation MPFunction (MPValue)
+
+- (instancetype)initWithTokenStream:(MPTokenStream *)tokenStream
+{
+    [tokenStream beginIgnoringWhitespaceTokens];
+    if (tokenStream.currentToken.tokenType != MPGenericFunctionToken) {
+        @throw [NSException exceptionWithName:NSInternalInconsistencyException reason:@"Expected Function" userInfo:nil];
+    }
+    [tokenStream endIgnoringOrAcceptingWhitespaceTokens];
+    return [self init];
+}
+
+- (NSArray *)expressionElements
+{
+    return @[self];
+}
+
+@end