Fundamental Redesign of Evaluation

MathPad/MPSumFunction.m

@@ -8,8 +8,8 @@
 
 #import "MPSumFunction.h"
 
+#import "MPSumFunctionTerm.h"
 #import "MPExpression.h"
-#import "MPExpressionTree.h"
 #import "MPEvaluationContext.h"
 
 
@@ -27,54 +27,16 @@ MPFunctionAccessorImplementation(SumExpression, _sumExpression)
     return @[@"startExpression", @"targetExpression", @"sumExpression"];
 }
 
-
-#pragma mark Evaluating Functions
-
-
-- (BOOL)validate:(NSError *__autoreleasing *)error
+- (BOOL)expectsVariableDefinitionInChildAtIndex:(NSUInteger)index
 {
-    MPExpressionTree *startTree = [self.startExpression parse];
-    if (![startTree validateExpectingVariableDefinition:YES error:error]) {
-        return NO;
-    }
-    
-    MPExpressionTree *targetTree = [self.targetExpression parse];
-    if (![targetTree validate:error]) {
-        return NO;
-    }
-    
-    [[MPEvaluationContext sharedContext] push];
-    [[MPEvaluationContext sharedContext] defineVariable:startTree.definedVariable withValue:[NSDecimalNumber notANumber]];
-    MPExpressionTree *sumTree = [self.sumExpression parse];
-    if (![sumTree validate:error]) {
-        return NO;
-    }
-    [[MPEvaluationContext sharedContext] pop];
-    return YES;
+    return index == 0;
 }
 
-
-- (NSDecimalNumber *)evaluate
+- (Class)functionTermClass
 {
-    MPExpressionTree *startTree = [self.startExpression parse];
-    NSDecimalNumber *start = [startTree evaluate];
-    NSDecimalNumber *target = [[self.targetExpression parse] evaluate];
-    MPExpressionTree *sumTree = [self.sumExpression parse];
-    
-    NSDecimalNumber *value = [NSDecimalNumber zero];
-    
-    [[MPEvaluationContext sharedContext] push];
-    for (NSDecimalNumber *current = start;
-         [current compare:target] <= 0;
-         current = [current decimalNumberByAdding:[[NSDecimalNumber alloc] initWithInteger:1]]) {
-        [[MPEvaluationContext sharedContext] defineVariable:startTree.definedVariable withValue:current];
-        value = [value decimalNumberByAdding:[sumTree evaluate]];
-    }
-    [[MPEvaluationContext sharedContext] pop];
-    return value;
+    return [MPSumFunctionTerm class];
 }
 
-
 #pragma mark Working With Functions