Fundamental Redesign of Evaluation

MathPad/MPVariable.m

@@ -8,63 +8,30 @@
 
 #import "MPVariable.h"
 
+#import "MPParsedExpression.h"
+
 #import "MPTokenStream.h"
 #import "MPToken.h"
 
 #import "MPExpression.h"
 #import "MPEvaluationContext.h"
 
-@implementation MPVariable {
-    NSRange _range;
-}
+@implementation MPVariable
 
-- (instancetype)init
+- (instancetype)initWithVariableName:(NSString *)variableName
 {
     self = [super init];
     if (self) {
+        NSAssert(variableName != nil, @"variableName must not be nil.");
+        _variableName = variableName;
     }
     return self;
 }
 
-- (instancetype)initWithTokenStream:(MPTokenStream *)tokenStream
+- (NSDecimalNumber *)doEvaluation:(NSError *__autoreleasing *)error
 {
-    self = [self init];
-    if (self) {
-        [tokenStream beginIgnoringWhitespaceTokens];
-        MPToken *token = tokenStream.currentToken;
-        if (token.tokenType == MPVariableToken) {
-            _variableName = token.stringValue;
-            _range = token.range;
-        } else {
-            @throw [NSException exceptionWithName:NSInternalInconsistencyException reason:@"Expected Variable" userInfo:nil];
-        }
-        [tokenStream currentTokenConsumed];
-        [tokenStream endIgnoringOrAcceptingWhitespaceTokens];
-    }
-    return self;
-}
-
-- (NSRange)range
-{
-    return _range;
-}
-
-- (BOOL)validate:(NSError *__autoreleasing *)error
-{
-    if (![[MPEvaluationContext sharedContext] isVariableDefined:self.variableName]) {
-        if (error) {
-            *error = MPParseError(9,
-                                  NSLocalizedString(@"Undefined Variable.", @"Error message. This is displayed when an expression contains an undefined variable."),
-                                  nil);
-        }
-        return NO;
-    }
-    return YES;
-}
-
-- (NSDecimalNumber *)evaluate
-{
-    return [[MPEvaluationContext sharedContext] valueForVariable:self.variableName];
+    return [self valueForVariable:self.variableName
+                            error:error];
 }
 
 @end