1 files changed, 13 insertions, 1 deletions
diff --git a/impl/Expression.hpp b/impl/Expression.hpp
index 0f3717f..cba9582 100644
--- a/impl/Expression.hpp
+++ b/impl/Expression.hpp
@@ -27,6 +27,10 @@ struct Expression {
     return NULL;
   }
 
+  virtual MaxExpression<Domain>* toMaxExpression() {
+    return NULL;
+  }
+
   virtual Domain eval(const VariableAssignment<Domain>&) const = 0;
   virtual Domain eval(const VariableAssignment<Domain>& rho,
                       const MaxStrategy<Domain>&) const {
@@ -106,6 +110,10 @@ struct OperatorExpression : public Expression<Domain> {
     return _operator.eval(argumentValues);
   }
 
+  std::vector<Expression<Domain>*>& arguments() {
+    return _arguments;
+  }
+
   const std::vector<Expression<Domain>*>& arguments() const {
     return _arguments;
   }
@@ -137,7 +145,7 @@ struct OperatorExpression : public Expression<Domain> {
   private:
   const Operator<Domain>& _operator;
   protected:
-  const std::vector<Expression<Domain>*> _arguments;
+  std::vector<Expression<Domain>*> _arguments;
 };
 
 template<typename Domain>
@@ -145,6 +153,10 @@ struct MaxExpression : public OperatorExpression<Domain> {
   MaxExpression(const unsigned int& id, const Maximum<Domain>& op, const std::vector<Expression<Domain>*>& arguments)
     : OperatorExpression<Domain>(op, arguments), _id(id) {}
 
+  MaxExpression* toMaxExpression() {
+    return this;
+  }
+
   const MaxExpression* toMaxExpression() const {
     return this;
   }