simplify postfix to tree transformation

alib2data/src/tree/common/TreeAuxiliary.h

@@ -84,26 +84,22 @@ ext::tree < common::ranked_symbol < SymbolType, RankType > > TreeAuxiliary::unra
 template < class SymbolType, class RankType >
 ext::tree < common::ranked_symbol < SymbolType, RankType > > TreeAuxiliary::postfixToTree ( const ext::vector < common::ranked_symbol < SymbolType, RankType > > & from ) {
-
 	std::stack < ext::tree < common::ranked_symbol < SymbolType, RankType > > > tree_stack;
-	for ( auto x : from ) {
+	for ( const common::ranked_symbol < SymbolType, RankType > & x : from ) {
 		if ( ( unsigned ) x.getRank ( ) == 0 ) {
-			tree_stack.push ( ext::tree < common::ranked_symbol < SymbolType, RankType > > ( common::ranked_symbol < SymbolType, RankType > ( x.getSymbol ( ), x.getRank ( ) ), ext::vector < ext::tree < common::ranked_symbol < SymbolType, RankType > > > ( ) ) );
+			tree_stack.push ( ext::tree < common::ranked_symbol < SymbolType, RankType > > ( x, ext::vector < ext::tree < common::ranked_symbol < SymbolType, RankType > > > ( ) ) );
 		} else {
-			unsigned children_size = ( unsigned ) x.getRank ( );
-			ext::list < ext::tree < common::ranked_symbol < SymbolType, RankType > > > childrenList;
-			for ( unsigned i = 0; i < children_size; ++i ) {
-				ext::tree < common::ranked_symbol < SymbolType, RankType > > child = tree_stack.top ( );
+			ext::vector < ext::tree < common::ranked_symbol < SymbolType, RankType > > > children;
+			for ( unsigned i = 0; i < ( unsigned ) x.getRank ( ); ++i ) {
+				children.push_back ( tree_stack.top ( ) );
 				tree_stack.pop ( );
-				childrenList.push_front ( child );
 			}
-			ext::vector < ext::tree < common::ranked_symbol < SymbolType, RankType > > > children {
-				std::begin ( childrenList ), std::end ( childrenList )
-			};
-			tree_stack.push ( ext::tree < common::ranked_symbol < SymbolType, RankType > > ( common::ranked_symbol < SymbolType, RankType > ( x.getSymbol ( ), x.getRank ( ) ), std::move ( children ) ) );
+			std::reverse ( children.begin ( ), children.end ( ) );
+
+			tree_stack.push ( ext::tree < common::ranked_symbol < SymbolType, RankType > > ( x, std::move ( children ) ) );
 		}
 	}