fixed problem with prefix of fresh variables

Former-commit-id: 1a7a87cfeb

src/storage/expressions/ExpressionManager.h

@@ -233,7 +233,7 @@ namespace storm {
              * @param prefix The prefix which should be used.
              * @return The variable.
              */
-            Variable declareFreshVariable(storm::expressions::Type const& variableType, bool auxiliary = false, std::string const& prefix = "x");
+            Variable declareFreshVariable(storm::expressions::Type const& variableType, bool auxiliary = false, std::string const& prefix = "_x");
             
             /*!
              * Declares a variable with rational type whose name is guaranteed to be unique and not yet in use.
@@ -242,7 +242,7 @@ namespace storm {
              * @param prefix The prefix which should be used.
              * @return The variable.
              */
-            Variable declareFreshRationalVariable(bool auxiliary = false, std::string const& prefix = "x");
+            Variable declareFreshRationalVariable(bool auxiliary = false, std::string const& prefix = "_x");
             
             /*!
              * Declares a variable with Boolean type whose name is guaranteed to be unique and not yet in use.
@@ -251,7 +251,7 @@ namespace storm {
              * @param prefix The prefix which should be used.
              * @return The variable.
              */
-            Variable declareFreshBooleanVariable(bool auxiliary = false, std::string const& prefix = "x");
+            Variable declareFreshBooleanVariable(bool auxiliary = false, std::string const& prefix = "_x");
             
             /*!
              * Declares a variable with integer type whose name is guaranteed to be unique and not yet in use.
@@ -260,7 +260,7 @@ namespace storm {
              * @param prefix The prefix which should be used.
              * @return The variable.
              */
-            Variable declareFreshIntegerVariable(bool auxiliary = false, std::string const& prefix = "x");
+            Variable declareFreshIntegerVariable(bool auxiliary = false, std::string const& prefix = "_x");
             
             /*!
              * Retrieves the number of variables.