Added Documentation

MathPad/MPExpressionTree.m

@@ -15,6 +15,8 @@
 
 #import "MPExpression.h"
 
+
+
 @implementation MPExpressionTree {
     NSMutableArray *_summands;
 }
@@ -28,6 +30,7 @@
     return self;
 }
 
+
 - (instancetype)initWithTokenStream:(MPTokenStream *)tokenStream
 {
     self = [self init];
@@ -51,17 +54,20 @@
     return self;
 }
 
+
 - (NSArray *)summands
 {
     return _summands;
 }
 
+
 - (BOOL)validate:(NSError *__autoreleasing *)error
 {
     return [self validateExpectingVariableDefinition:NO
                                                error:error];
 }
 
+
 - (BOOL)validateExpectingVariableDefinition:(BOOL)flag
                                       error:(NSError *__autoreleasing *)error
 {
@@ -100,6 +106,7 @@
     return YES;
 }
 
+
 - (NSDecimalNumber *)evaluate
 {
     NSDecimalNumber *value = [NSDecimalNumber zero];