Added the MPExpressionTree Classes

MathPad/MPSumFunction.m

@@ -9,12 +9,8 @@
 #import "MPSumFunction.h"
 #import "MPExpression.h"
 
-#import "MPExpressionEvaluator.h"
 #import "MPEvaluationContext.h"
 
-// TODO: Use this macro elsewhere
-#define ReturnIfNil(test) if(test == nil) return nil
-
 @implementation MPSumFunction
 
 MPFunctionAccessorImplementation(StartExpression, _startExpression)
@@ -27,42 +23,47 @@ MPFunctionAccessorImplementation(SumExpression, _sumExpression)
 }
 
 #pragma mark Evaluating Functions
-- (MPTerm *)parseWithError:(MPParseError *__autoreleasing *)error
-{
-    MPExpressionEvaluator *startEvaluator = [[MPExpressionEvaluator alloc] initWithExpression:self.startExpression];
-    MPTerm *start = [startEvaluator parseExpectingVariable:YES
-                                                     error:error];
-    ReturnIfNil(start);
 
-    MPExpressionEvaluator *targetEvaluator = [[MPExpressionEvaluator alloc] initWithExpression:self.targetExpression];
-    MPTerm *target = [targetEvaluator parseExpectingVariable:NO
-                                                       error:error];
-    ReturnIfNil(target);
+- (BOOL)validate:(MPParseError *__autoreleasing *)error
+{
+    MPExpressionTree *startTree = [self.startExpression parse];
+    if (![startTree validateExpectingVariableDefinition:YES error:error]) {
+        return NO;
+    }
     
-    NSString *variable = startEvaluator.definedVariable.copy;
+    MPExpressionTree *targetTree = [self.targetExpression parse];
+    if (![targetTree validate:error]) {
+        return NO;
+    }
     
     [[MPEvaluationContext sharedContext] push];
-    [[MPEvaluationContext sharedContext] defineVariable:variable withValue:[NSNull null]];
-    MPExpressionEvaluator *sumEvaluator = [[MPExpressionEvaluator alloc] initWithExpression:self.sumExpression];
-    MPTerm *sum = [sumEvaluator parseExpectingVariable:NO
-                                                 error:error];
-    ReturnIfNil(sum);
+    [[MPEvaluationContext sharedContext] defineVariable:startTree.definedVariable withValue:[NSDecimalNumber notANumber]];
+    MPExpressionTree *sumTree = [self.sumExpression parse];
+    if (![sumTree validate:error]) {
+        return NO;
+    }
     [[MPEvaluationContext sharedContext] pop];
+    return YES;
+}
+
+- (NSDecimalNumber *)evaluate
+{
+    MPExpressionTree *startTree = [self.startExpression parse];
+    NSDecimalNumber *start = [startTree evaluate];
+    NSDecimalNumber *target = [[self.targetExpression parse] evaluate];
+    MPExpressionTree *sumTree = [self.sumExpression parse];
     
-    return [[MPTerm alloc] initWithBlock:^NSDecimalNumber *{
-        [[MPEvaluationContext sharedContext] push];
-        NSDecimalNumber *value = [NSDecimalNumber zero];
-        NSDecimalNumber *startValue = [start evaluate];
-        NSDecimalNumber *targetValue = [target evaluate];
-        for (NSDecimalNumber *iterator = startValue;
-             [iterator compare:targetValue] <= 0 ;
-             iterator = [iterator decimalNumberByAdding:[[NSDecimalNumber alloc] initWithInteger:1]]) {
-            [[MPEvaluationContext sharedContext] defineVariable:variable withValue:iterator];
-            value = [value decimalNumberByAdding:[sum evaluate]];
-        }
-        [[MPEvaluationContext sharedContext] pop];
-        return value;
-    }];
+    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;
 }
 
 #pragma mark Working With Functions