Redesign of the Evaluation System

MathPad/MPExpressionEvaluator.m

@@ -9,6 +9,8 @@
 #import "MPExpressionEvaluator.h"
 #import "MPExpression.h"
 #import "MPFunction.h"
+#import "MPParsedFactor.h"
+#import "MPFunction+MPParsedFactor.h"
 
 @interface MPExpressionEvaluator ()
 @property (readwrite, nonatomic, strong) NSString *definedVariable;
@@ -16,7 +18,6 @@
 @end
 
 @implementation MPExpressionEvaluator {
-    NSMutableDictionary *_variableBindings;
     MPElementParser *parser;
 }
 - (id)initWithExpression:(MPExpression *)expression
@@ -24,29 +25,12 @@
     self = [super init];
     if (self) {
         _expression = expression;
-        _variableBindings = [[NSMutableDictionary alloc] init];
         parser = [[MPElementParser alloc] init];
     }
     return self;
 }
 
 #pragma mark Evaluating Expressions
-- (NSDictionary *)variableBindings
-{
-    return [_variableBindings copy];
-}
-
-- (void)bindValue:(NSDecimalNumber *)value toVariableName:(NSString *)name
-{
-    [_variableBindings setObject:value
-                          forKey:name];
-}
-
-- (void)unbindVariableName:(NSString *)name
-{
-    [_variableBindings removeObjectForKey:name];
-}
-
 - (NSDecimalNumber *)evaluateWithError:(MPParseError *__autoreleasing *)error
 {
     return [self evaluateVariableDefinition:NO error:error];
@@ -68,14 +52,10 @@
         id<MPExpressionElement> element = [self.expression elementAtIndex:elementIndex];
         
         if ([element isString]) {
-            MPParsedFactor *nextFactor = nil;
+            id<MPParsedFactor> nextFactor = nil;
             if (elementIndex < self.expression.numberOfElements - 1) {
                 MPFunction *nextFunction = (MPFunction *)[self.expression elementAtIndex:elementIndex+1];
-                NSDecimalNumber *functionValue = [nextFunction evaluate:error];
-                if (!functionValue) {
-                    return nil;
-                }
-                nextFactor = [MPParsedFactor factorWithDecimalNumber:functionValue];
+                nextFactor = nextFunction;
             }
             
             NSArray *newProducts;
@@ -105,14 +85,10 @@
             
             elementIndex++;
         } else {
-            NSDecimalNumber *functionValue = [(MPFunction *)element evaluate:error];
-            if (!functionValue) {
-                return nil;
-            }
             if (!currentProduct) {
                 currentProduct = [[MPParsedProduct alloc] init];
             }
-            [currentProduct addFactor:[MPParsedFactor factorWithDecimalNumber:functionValue]];
+            [currentProduct addFactor:(MPFunction *)element];
         }
     }
     
@@ -120,7 +96,11 @@
     
     NSDecimalNumber *value = [NSDecimalNumber zero];
     for (MPParsedProduct *product in products) {
-        value = [value decimalNumberByAdding:product.value];
+        NSDecimalNumber *productValue = [product evaluateWithError:error];
+        if (!productValue) {
+            return nil;
+        }
+        value = [value decimalNumberByAdding:productValue];
     }
     return value;
 }