diff --git a/src/SQLParserResult.h b/src/SQLParserResult.h
index 96e19cf..0e4e562 100644
--- a/src/SQLParserResult.h
+++ b/src/SQLParserResult.h
@@ -15,7 +15,7 @@ namespace hsql {
     // Takes ownership of the statement.
     SQLParserResult(SQLStatement* stmt);
 
-    // Deletes all statements in the resul.
+    // Deletes all statements in the result.
     virtual ~SQLParserResult();
 
     // Returns true if parsing was successful.
@@ -40,7 +40,7 @@ namespace hsql {
     SQLStatement* getMutableStatement(int index);
 
     // Adds a statement to the result list of statements.
-    // Takes ownership of the statement.
+    // SQLParserResult takes ownership of the statement.
     void addStatement(SQLStatement* stmt);
 
     // Set whether parsing was successful.
diff --git a/src/sql/Expr.cpp b/src/sql/Expr.cpp
index 40209ab..1345714 100644
--- a/src/sql/Expr.cpp
+++ b/src/sql/Expr.cpp
@@ -155,32 +155,32 @@ namespace hsql {
     return e;
   }
 
-  bool Expr::isType(ExprType e_type) {
-    return e_type == type;
+  bool Expr::isType(ExprType exprType) const {
+    return exprType == type;
   }
 
-  bool Expr::isLiteral() {
+  bool Expr::isLiteral() const {
     return isType(kExprLiteralInt) || isType(kExprLiteralFloat) || isType(kExprLiteralString) || isType(kExprPlaceholder);
   }
 
-  bool Expr::hasAlias() {
+  bool Expr::hasAlias() const {
     return alias != NULL;
   }
 
-  bool Expr::hasTable() {
+  bool Expr::hasTable() const {
     return table != NULL;
   }
 
-  char* Expr::getName() {
+  const char* Expr::getName() const {
     if (alias != NULL) return alias;
     else return name;
   }
 
-  bool Expr::isSimpleOp() {
+  bool Expr::isSimpleOp() const {
     return opType == kOpSimple;
   }
 
-  bool Expr::isSimpleOp(char op) {
+  bool Expr::isSimpleOp(char op) const {
     return isSimpleOp() && opChar == op;
   }
 
diff --git a/src/sql/Expr.h b/src/sql/Expr.h
index 810895b..536bd31 100644
--- a/src/sql/Expr.h
+++ b/src/sql/Expr.h
@@ -36,7 +36,7 @@ namespace hsql {
     kOpCase,
 
     // Binary operators.
-    // Simple operators are identified by the opChar field (e.g. =, >, <).
+    // Simple operators are identified by the opChar field (e.g. +, -, =, >, <).
     kOpSimple,
 
     kOpNotEquals,
@@ -60,13 +60,9 @@ namespace hsql {
   // Represents SQL expressions (i.e. literals, operators, column_refs).
   // TODO: When destructing a placeholder expression, we might need to alter the placeholder_list.
   struct Expr {
-    
-    Expr(ExprType type);
 
-    // Interesting side-effect:
-    // Making the destructor virtual used to cause segmentation faults.
-    // TODO: inspect.
-    ~Expr();
+    Expr(ExprType type);
+    virtual ~Expr();
 
     ExprType type;
 
@@ -89,19 +85,19 @@ namespace hsql {
 
     // Convenience accessor methods.
 
-    bool isType(ExprType e_type);
+    bool isType(ExprType exprType) const;
 
-    bool isLiteral();
+    bool isLiteral() const;
 
-    bool hasAlias();
+    bool hasAlias() const;
 
-    bool hasTable();
+    bool hasTable() const;
 
-    char* getName();
+    const char* getName() const;
 
-    bool isSimpleOp();
+    bool isSimpleOp() const;
 
-    bool isSimpleOp(char op);
+    bool isSimpleOp(char op) const;
 
 
     // Static constructors.
diff --git a/src/sql/SelectStatement.h b/src/sql/SelectStatement.h
index bb60836..7606e68 100644
--- a/src/sql/SelectStatement.h
+++ b/src/sql/SelectStatement.h
@@ -13,7 +13,6 @@ namespace hsql {
 
   /**
    * Description of the order by clause within a select statement
-   * TODO: hold multiple expressions to be sorted by
    */
   struct OrderDescription {
     OrderDescription(OrderType type, Expr* expr);
@@ -41,8 +40,7 @@ namespace hsql {
    */
   struct GroupByDescription {
     GroupByDescription();
-    // TODO: make virtual
-    ~GroupByDescription();
+    virtual ~GroupByDescription();
 
     std::vector<Expr*>* columns;
     Expr* having;
diff --git a/src/sql/Table.h b/src/sql/Table.h
index 58ecca4..745d5f1 100644
--- a/src/sql/Table.h
+++ b/src/sql/Table.h
@@ -35,10 +35,10 @@ namespace hsql {
     JoinDefinition* join;
 
     // Returns true if a schema is set.
-    bool hasSchema();
+    bool hasSchema() const;
 
     // Returns the alias, if it is set. Otherwise the name.
-    char* getName();
+    const char* getName() const;
   };
 
   // Possible types of joins.
diff --git a/src/sql/statements.cpp b/src/sql/statements.cpp
index 69ffc84..75b794f 100644
--- a/src/sql/statements.cpp
+++ b/src/sql/statements.cpp
@@ -268,11 +268,11 @@ namespace hsql {
     }
   }
 
-  bool TableRef::hasSchema() {
+  bool TableRef::hasSchema() const {
     return schema != NULL;
   }
 
-  char* TableRef::getName() {
+  const char* TableRef::getName() const {
     if (alias != NULL) return alias;
     else return name;
   }