introduce ext::visit

alib2common/src/object/Object.h

@@ -44,7 +44,7 @@ class Object {
 			return Object ( std::forward < decltype ( element ) > ( element ) );
 		};
-		return std::visit ( visitor, std::forward < Variant > ( data ) );
+		return ext::visit ( visitor, std::forward < Variant > ( data ) );
 	}
 	/**

alib2std/src/extensions/container/variant.hpp

@@ -38,6 +38,24 @@
 namespace ext {
+template < class Visitor, class... Variants >
+constexpr auto visit ( Visitor && vis, Variants && ... vars ) {
+	auto extToStd = [] ( auto && variant ) {
+		using __std__variant = typename std::decay_t < decltype ( variant ) >::__std__variant;
+
+		if constexpr ( std::is_lvalue_reference_v < decltype ( variant ) > && std::is_const_v < std::remove_reference_t < decltype ( variant ) > > ) {
+			return static_cast < const __std__variant & > ( variant );
+		} else if constexpr ( std::is_lvalue_reference_v < decltype ( variant ) > ) {
+			return static_cast < __std__variant & > ( variant );
+		} else if constexpr ( std::is_rvalue_reference_v < decltype ( variant ) > ) {
+			return static_cast < __std__variant && > ( variant );
+		} else {
+			static_assert ( "Unhandled option" );
+		}
+	};
+
+	return std::visit ( std::forward < Visitor > ( vis ), extToStd ( std::forward < Variants > ( vars ) ) ... );
+}
 /**
  * \brief
  * Class to help building of the variant type or, in case variant is requested to be constructed from single type or more types but all the same, that concrete type.
@@ -243,7 +261,7 @@ public:
 	 * \return negative value if this is smaller than the other instance, positive if this is greater than the other instance, zero othervise
 	 */
 	int compare ( const variant < Ts ... > & other ) const {
-		return std::visit ( VariantCompare ( other ), * this );
+		return ext::visit ( VariantCompare ( other ), * this );
 	}
 	/**
@@ -258,7 +276,7 @@ public:
 	 */
 	template < typename T, typename std::enable_if < ext::is_in < T, Ts ... >::value >::type * = nullptr >
 	int compare ( const T & other ) const {
-		return std::visit ( VariantCompare2 < T > ( other ), * this );
+		return ext::visit ( VariantCompare2 < T > ( other ), * this );
 	}
 	/**
@@ -358,7 +376,7 @@ public:
 	 */
 	template < class Result, class Callable >
 	Result call ( Callable callable ) const {
-		return std::visit ( callable, * this );
+		return ext::visit ( callable, * this );
 	}
 	/**

alib2str/src/container/string/ObjectsVariant.h

@@ -59,7 +59,7 @@ bool stringApi < ext::variant < Types ... > >::first ( std::istream & input ) {
 template < class ... Types >
 void stringApi < ext::variant < Types ... > >::compose ( std::ostream & output, const ext::variant < Types ... > & container ) {
-	std::visit ( VariantStringApiCallback ( output ), container );
+	ext::visit ( VariantStringApiCallback ( output ), container );
 }
 } /* namespace core */