Added default constructor values to classes for Parser.

Parserv3.h

@@ -14,6 +14,7 @@ class Relation
 	public: 
 		Relation()
 		{
+			name = NULL;
 		}
 		
 		Relation(string str)
@@ -36,6 +37,11 @@ class Attribute
 	string name;
 	
 	public:
+		Attribute()
+		{
+			name = NULL;
+		}
+		
 		Attribute(string str)
 		{
 			name = str;
@@ -58,6 +64,12 @@ class Union
 	string Un2;
 	
 	public:
+		Union()
+		{
+			Un1 = NULL;
+			Un2 = NULL;
+		}
+		
 		Union (string s1, string s2)
 		{
 			Un1 = s1;
@@ -76,6 +88,12 @@ class Product
 	string Pr2;
 	
 	public:
+		Product()
+		{
+			Pr1 = NULL;
+			Pr2 = NULL;
+		}
+		
 		Product(string s1, string s2)
 		{
 			Pr1 = s1;
@@ -94,6 +112,12 @@ class Difference
 	string D2;
 	
 	public:
+		Difference()
+		{
+			D1 = NULL;
+			D2 = NULL;
+		}
+		
 		Difference(string s1, string s2)
 		{
 			D1 = s1;
@@ -112,6 +136,12 @@ class Renaming
 	string oldName;
 	
 	public:
+		Renaming()
+		{
+			newName = NULL;
+			oldName = NULL;
+		}
+		
 		Renaming(string s1, string s2)
 		{
 			newName = s1;
@@ -130,6 +160,12 @@ class Projection
 	string oldName;
 	
 	public:
+		Projection()
+		{
+			newName = NULL;
+			oldName = NULL;
+		}
+		
 		Projection(string s1, string s2)
 		{
 			newName = s1;
@@ -150,6 +186,7 @@ class Operand
 	
 		Operand()
 		{
+			op = NULL;
 		}
 		
 		Operand(string str)
@@ -175,6 +212,7 @@ class Op
 	public: 
 		Op()
 		{
+			op = NULL;
 		}
 		
 		Op(string str)
@@ -200,6 +238,12 @@ class Comparison
 	Operand operand2;
 	
 	public:
+		Comparison()
+		{
+			op = NULL;
+			operand1 = NULL;
+			operand2 = NULL;
+		}
 		
 		Comparison(string str1, string str2, string str3)
 		{
@@ -225,6 +269,11 @@ class Conjunction
 {
 	string conj;
 	public:
+		Conjunction()
+		{
+			conj = NULL;
+		}
+		
 		Conjunction(string str)
 		{
 			conj = str;
@@ -248,6 +297,7 @@ class Condition
 	
 		Condition()
 		{
+			cond = NULL;
 		}
 	
 		Condition(string str)
@@ -270,6 +320,11 @@ class Selection
 {
 	string select;
 	public:
+		Selection()
+		{
+			select = NULL;
+		}
+		
 		Selection(string str)
 		{
 			select = str;
@@ -289,6 +344,7 @@ class Expression
 	
 		Expression()
 		{
+			exp = NULL;
 		}
 	
 		Expression(string str)