diff --git a/src/lib/Expr.h b/src/lib/Expr.h
index b66dac3..3a3f0e5 100644
--- a/src/lib/Expr.h
+++ b/src/lib/Expr.h
@@ -28,11 +28,13 @@ typedef struct Expr Expr;
 /** 
  * @class Expr
  * @brief 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 {
 	/**
 	 * Operator types. These are important for expressions of type kExprOperator
-	 * Trivial types are those that can be descriped by a sigle character e.g:
+	 * Trivial types are those that can be described by a single character e.g:
 	 * + - * / < > = %
 	 * Non-trivial are:
 	 * <> <= >= LIKE ISNULL NOT
@@ -64,8 +66,8 @@ struct Expr {
 		alias(NULL) {};
 
 	// Interesting side-effect:
-	// Making the destructor virtual causes segmentation faults
-	~Expr();
+	// Making the destructor virtual used to cause segmentation faults
+	Expr();
 	
 	ExprType type;
 
diff --git a/src/parser/bison_parser.y b/src/parser/bison_parser.y
index 531f082..3ed1f7b 100644
--- a/src/parser/bison_parser.y
+++ b/src/parser/bison_parser.y
@@ -498,7 +498,6 @@ opt_where:
 	|	/* empty */ { $$ = NULL; }
 	;
 
-// TODO: having
 opt_group:
 		GROUP BY expr_list opt_having {
 			$$ = new GroupByDescription();
@@ -626,7 +625,7 @@ star_expr:
 		'*' { $$ = new Expr(kExprStar); }
 	;
 
-/* TODO: keep list of placeholders */
+
 placeholder_expr:
 		'?' {
 			$$ = Expr::makePlaceholder(yylloc.total_column);