Added the MPExpressionTree Classes

MathPad/MPExpressionTree.m

@@ -0,0 +1,158 @@
+//
+//  MPExpressionTree.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 09.10.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPExpressionTree.h"
+
+@implementation MPExpressionTree {
+    NSRange _variableDefinitionRange;
+    NSMutableArray *_summands;
+    NSRange _range;
+}
+
+- (id)init
+{
+    self = [super init];
+    if (self) {
+        _summands = [[NSMutableArray alloc] init];
+    }
+    return self;
+}
+
+- (instancetype)initWithTokenStream:(MPTokenStream *)tokenStream
+{
+    self = [self init];
+    if (self) {
+        MPTokenStreamRecordCurrentLocation(tokenStream);
+        
+        [tokenStream beginIgnoringWhitespaceTokens];
+        
+        _variableDefinitionRange = NSMakeRange(NSNotFound, 0);
+        self.definedVariable = nil;
+        if (tokenStream.currentToken.tokenType == MPVariableToken) {
+            if (tokenStream.peekNextToken.tokenType == MPEqualsToken) {
+                self.definedVariable = tokenStream.currentToken.stringValue;
+                NSRange variableRange = tokenStream.currentToken.range;
+                [tokenStream currentTokenConsumed];
+                NSRange equalsRange = tokenStream.currentToken.range;
+                [tokenStream currentTokenConsumed];
+                _variableDefinitionRange = NSUnionRange(variableRange, equalsRange);
+            }
+        }
+        while ([tokenStream hasMoreTokens]) {
+            [_summands addObject:[[MPSummand alloc] initWithTokenStream:tokenStream]];
+        }
+        
+        [tokenStream endIgnoringOrAcceptingWhitespaceTokens];
+        _range = MPTokenStreamRecordedRange(tokenStream);
+    }
+    return self;
+}
+
+- (NSRange)range
+{
+    return _range;
+}
+
+- (BOOL)validate:(MPParseError *__autoreleasing *)error
+{
+    return [self validateExpectingVariableDefinition:NO
+                                               error:error];
+}
+
+- (BOOL)validateExpectingVariableDefinition:(BOOL)flag
+                                      error:(MPParseError *__autoreleasing *)error
+{
+    if (flag) {
+        if (!self.definedVariable) {
+            if (error) {
+                *error = MPParseError(NSMakeRange(self.range.location, 0), @"Expected Variable Definition.");
+            }
+            return NO;
+        }
+    } else {
+        if (self.definedVariable) {
+            if (error) {
+                *error = MPParseError(_variableDefinitionRange, @"Unexpected Variable Definition");
+            }
+            return NO;
+        }
+    }
+    if (_summands.count == 0) {
+        if (error) {
+            *error = MPParseError(self.range, @"Empty Expression.");
+        }
+        return NO;
+    }
+    for (MPSummand *summand in _summands) {
+        if (![summand validate:error]) {
+            return NO;
+        }
+    }
+    return YES;
+}
+
+- (NSDecimalNumber *)evaluate
+{
+    NSDecimalNumber *value = [NSDecimalNumber zero];
+    for (MPSummand *summand in _summands) {
+        NSDecimalNumber *currentValue = [summand evaluate];
+        if ([currentValue isEqualToNumber:[NSDecimalNumber notANumber]]) {
+            value = currentValue;
+            break;
+        }
+        value = [value decimalNumberByAdding:currentValue];
+    }
+    return value;
+}
+
+
+- (NSArray *)expressionElements
+{
+    NSMutableArray *elements = [[NSMutableArray alloc] init];
+    if (self.definedVariable) {
+        [elements addObject:[NSString stringWithFormat:@"%@=", self.definedVariable]];
+    }
+    for (MPSummand *summand in _summands) {
+        [elements addObjectsFromArray:summand.expressionElements];
+    }
+    return elements;
+}
+
+- (NSArray *)summands
+{
+    return _summands;
+}
+
+- (void)appendSummand:(MPSummand *)summand
+{
+    [_summands addObject:summand];
+}
+
+- (void)insertSummand:(MPSummand *)summand
+              atIndex:(NSUInteger)index
+{
+    [_summands insertObject:summand
+                    atIndex:index];
+}
+
+- (void)removeSummand:(MPSummand *)summand
+{
+    [_summands removeObject:summand];
+}
+
+- (void)removeSummandAtIndex:(NSUInteger)index
+{
+    [_summands removeObjectAtIndex:index];
+}
+
+- (MPSummand *)summandAtIndex:(NSUInteger)index
+{
+    return [_summands objectAtIndex:index];
+}
+
+@end