Fundamental Redesign of Evaluation

MathPad/MPPowerTerm.m

@@ -0,0 +1,36 @@
+//
+//  MPPowerTerm.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 15.11.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPPowerTerm.h"
+#import "MPParsedExpression.h"
+
+@implementation MPPowerTerm
+
+- (NSDecimalNumber *)doEvaluation:(NSError *__autoreleasing *)error
+{
+    NSDecimalNumber *exponent = [[self expressionAtIndex:0] evaluate:error];
+    if (!exponent) {
+        return nil;
+    }
+    NSDecimalNumber *base = [self.baseTerm evaluate:error];
+    if (!base) {
+        return nil;
+    }
+    if ([base isEqualToNumber:@(0)] && [exponent isEqualToNumber:@(0)]) {
+        // The C pow function returns 1 for pow(0, 0). Mathematically this should be undefined.
+        if (error) {
+            *error = [NSError errorWithDomain:MPMathKitErrorDomain
+                                         code:101
+                                     userInfo:@{NSLocalizedDescriptionKey: NSLocalizedString(@"0 to the power of 0 is undefined.", nil)}];
+        }
+        return nil;
+    }
+    return [[NSDecimalNumber alloc] initWithDouble:pow(base.doubleValue, exponent.doubleValue)];
+}
+
+@end