Redesign of the Evaluation System

MathPad/MPParsedVariable.m

@@ -0,0 +1,47 @@
+//
+//  MPParsedVariable.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 13.09.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPParsedVariable.h"
+#import "MPEvaluationContext.h"
+
+@interface MPParsedVariable ()
+@property (nonatomic) NSRange range;
+@property (nonatomic, strong) NSString *variableName;
+@end
+
+@implementation MPParsedVariable
+
+- (instancetype)initWithRange:(NSRange)range
+                     inString:(NSString *)string
+{
+    self = [super init];
+    if (self) {
+        _range = range;
+        if (range.location != NSNotFound) {
+            _variableName = [string substringWithRange:range];
+        }
+    }
+    return self;
+}
+
+- (BOOL)exists
+{
+    return self.range.location != NSNotFound;
+}
+
+- (NSDecimalNumber *)evaluateWithError:(MPParseError *__autoreleasing *)error
+{
+    NSDecimalNumber *value = [[MPEvaluationContext sharedContext] valueForVariableName:self.variableName];
+    if (!value) {
+        *error = MPParseError(self.range, @"Undefined Variable.");
+        return nil;
+    }
+    return value;
+}
+
+@end