Reorganized File Structure

Added Documentation

MathKit/MPSumTerm.m

@@ -0,0 +1,42 @@
+//
+//  MPSumTerm.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 14.11.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPSumTerm.h"
+
+#import "MPParsedExpression.h"
+#import "MPProductTerm.h"
+
+#import "MPToken.h"
+
+@implementation MPSumTerm
+
+- (instancetype)initWithSummands:(NSArray *)summands
+{
+    self = [super init];
+    if (self) {
+        NSAssert(summands != nil, @"summands must not be nil.");
+        NSAssert(summands.count > 0, @"summands must not be empty.");
+        _summands = summands;
+    }
+    return self;
+}
+
+- (NSDecimalNumber *)doEvaluation:(NSError *__autoreleasing *)error
+{
+    NSDecimalNumber *value = [NSDecimalNumber zero];
+    for (MPTerm *summand in self.summands) {
+        NSDecimalNumber *currentValue = [summand evaluate:error];
+        if (!currentValue) {
+            return nil;
+        }
+        value = [value decimalNumberByAdding:currentValue];
+    }
+    return value;
+}
+
+@end