Redesign of the Evaluation System

MathPad/MPSumFunction.m

@@ -10,6 +10,7 @@
 #import "MPExpression.h"
 
 #import "MPExpressionEvaluator.h"
+#import "MPEvaluationContext.h"
 
 @implementation MPSumFunction
 
@@ -99,7 +100,7 @@
 }
 
 #pragma mark Evaluating Functions
-- (NSDecimalNumber *)evaluate:(MPParseError *__autoreleasing *)error
+- (NSDecimalNumber *)evaluateWithError:(MPParseError *__autoreleasing *)error
 {
     MPExpressionEvaluator *startEvaluator = self.startExpression.evaluator;
     NSDecimalNumber *start = [startEvaluator evaluateVariableDefinition:YES error:error];
@@ -111,10 +112,12 @@
         return nil;
     }
     
+    [[MPEvaluationContext sharedContext] push];
+    
     MPExpressionEvaluator *sumEvaluator = self.sumExpression.evaluator;
     NSDecimalNumber *value = [NSDecimalNumber zero];
     for (NSDecimalNumber *iterator = start; [iterator compare:target] <= 0; iterator = [iterator decimalNumberByAdding:[[NSDecimalNumber alloc] initWithInteger:1]]) {
-        [sumEvaluator bindValue:iterator toVariableName:startEvaluator.definedVariable];
+        [[MPEvaluationContext sharedContext] bindValue:iterator toName:startEvaluator.definedVariable];
         NSDecimalNumber *summand = [sumEvaluator evaluateWithError:error];
         if (summand) {
             value = [value decimalNumberByAdding:summand];
@@ -122,6 +125,9 @@
             return nil;
         }
     }
+    
+    [[MPEvaluationContext sharedContext] pop];
+    
     return value;
 }