removed non const ref() function

exprtk.hpp

@@ -7586,11 +7586,17 @@ namespace exprtk
          {
              *value_ = val;
          }
-#endif
+
+         inline T* value_ptr()
+         {
+             return value_;
+         }
+#else
          inline T& ref() exprtk_override
          {
              return (*value_);
          }
+#endif
 
       	 inline const T& ref() const exprtk_override
          {
@@ -8183,8 +8189,15 @@ namespace exprtk
 
          inline T value() const exprtk_override
          {
+#ifdef exprtk_enable_vector_runtime_checks
+            const T tmp = var1_->ref();
+            var1_->set(var0_->ref());
+            var0_->set(tmp);
+            return tmp;
+#else
             std::swap(var0_->ref(),var1_->ref());
             return var1_->ref();
+#endif
          }
 
          inline typename expression_node<T>::node_type type() const exprtk_override
@@ -10458,9 +10471,13 @@ namespace exprtk
             if (var_node_ptr_)
             {
                assert(branch(1));
-
+#ifdef exprtk_enable_vector_runtime_checks
+               T result = branch(1)->value();
+               var_node_ptr_->set(result);
+#else
                T& result = var_node_ptr_->ref();
                result = branch(1)->value();
+#endif
 
                return result;
             }
@@ -12742,7 +12759,7 @@ namespace exprtk
                      return false;
 
                   ts.size = 1;
-                  ts.data = &var->ref();
+                  ts.data = var->value_ptr();
                   ts.type = type_store_t::e_scalar;
                }
                else
@@ -37795,12 +37812,21 @@ namespace exprtk
 
       if (var)
       {
+#ifdef exprtk_enable_vector_runtime_checks
+          T& x = *(var->value_ptr());
+          const T x_original = x;
+          const T result = integrate(e, x, r0, r1, number_of_intervals);
+          var->set(x_original);
+
+          return result;
+#else
          T& x = var->ref();
          const T x_original = x;
          const T result = integrate(e, x, r0, r1, number_of_intervals);
          x = x_original;
 
          return result;
+#endif
       }
       else
          return std::numeric_limits<T>::quiet_NaN();
@@ -37886,12 +37912,21 @@ namespace exprtk
 
       if (var)
       {
+#ifdef exprtk_enable_vector_runtime_checks
+         T& x = *(var->value_ptr());
+         const T x_original = x;
+         const T result = derivative(e, x, h);
+         var->set(x_original);
+
+         return result;
+#else
       	 T& x = var->ref();
          const T x_original = x;
          const T result = derivative(e, x, h);
          x = x_original;
 
          return result;
+#endif
       }
       else
          return std::numeric_limits<T>::quiet_NaN();
@@ -37913,12 +37948,21 @@ namespace exprtk
 
       if (var)
       {
+#ifdef exprtk_enable_vector_runtime_checks
+         T &x = *(var->value_ptr());
+         const T x_original = x;
+         const T result = second_derivative(e, x, h);
+         var->set(x_original);
+
+         return result;
+#else         
          T& x = var->ref();
          const T x_original = x;
          const T result = second_derivative(e, x, h);
          x = x_original;
 
          return result;
+#endif
       }
       else
          return std::numeric_limits<T>::quiet_NaN();
@@ -37940,12 +37984,21 @@ namespace exprtk
 
       if (var)
       {
+#ifdef exprtk_enable_vector_runtime_checks
+         T &x = *(var->value_ptr());
+         const T x_original = x;
+         const T result = third_derivative(e, x, h);
+         var->set(x_original);
+
+         return result;
+#else
          T& x = var->ref();
          const T x_original = x;
          const T result = third_derivative(e, x, h);
          x = x_original;
 
          return result;
+#endif
       }
       else
          return std::numeric_limits<T>::quiet_NaN();