Define and use utilities transform_range, transform_container

src/Internat.cpp

@@ -303,8 +303,8 @@ wxString Internat::StripAccelerators(const wxString &s)
 wxArrayString LocalizedStrings(
    const ComponentInterfaceSymbol strings[], size_t nStrings)
 {
-   wxArrayString results;
-   std::transform( strings, strings + nStrings, std::back_inserter(results),
-                   std::mem_fn( &ComponentInterfaceSymbol::Translation ) );
-   return results;
+   return transform_range<wxArrayString>(
+      strings, strings + nStrings,
+      std::mem_fn( &ComponentInterfaceSymbol::Translation )
+   );
 }

src/MemoryX.h

@@ -640,4 +640,20 @@ namespace std
 }
 #endif
 
+// A utility function building a container of results
+template< typename Container, typename Iterator, typename Function >
+Container transform_range( Iterator first, Iterator last, Function &&fn )
+{
+   Container result;
+   std::transform( first, last, std::back_inserter( result ), fn );
+   return result;
+}
+// A utility function, often constructing a vector from another vector
+template< typename OutContainer, typename InContainer, typename Function >
+OutContainer transform_container( InContainer &inContainer, Function &&fn )
+{
+   return transform_range<OutContainer>(
+      inContainer.begin(), inContainer.end(), fn );
+}
+
 #endif // __AUDACITY_MEMORY_X_H__

src/Track.cpp

@@ -1152,22 +1152,17 @@ namespace {
    Array GetTypedTracks(const TrackRange &trackRange,
                        bool selectionOnly, bool includeMuted)
    {
-      Array array;
-
-      using Type = typename
-         std::remove_reference< decltype( *array[0] ) >::type;
+      using Type = typename std::remove_reference<
+         decltype( *std::declval<Array>()[0] )
+      >::type;
       auto subRange =
          trackRange.template Filter<Type>();
       if ( selectionOnly )
          subRange = subRange + &Track::IsSelected;
       if ( ! includeMuted )
          subRange = subRange - &Type::GetMute;
-      std::transform(
-         subRange.begin(), subRange.end(), std::back_inserter( array ),
-         []( Type *t ){ return Track::Pointer<Type>( t ); }
-      );
-
-      return array;
+      return transform_range<Array>( subRange.begin(), subRange.end(),
+          []( Type *t ){ return Track::Pointer<Type>( t ); } );
    }
 }
 

src/ondemand/ODDecodeFFmpegTask.cpp

@@ -111,20 +111,13 @@ private:
 
 auto ODDecodeFFmpegTask::FromList( const TrackHolders &channels ) -> Streams
 {
-   Streams streams;
-   streams.reserve(channels.size());
-   using namespace std;
-   transform(channels.begin(), channels.end(), back_inserter(streams),
+   // Convert array of array of unique_ptr to array of array of bare pointers
+   return transform_container<Streams>( channels,
       [](const NewChannelGroup &holders) {
-         Channels channels;
-         channels.reserve(holders.size());
-         transform(holders.begin(), holders.end(), back_inserter(channels),
-            mem_fn(&NewChannelGroup::value_type::get)
-         );
-         return channels;
+         return transform_container<Channels>( holders,
+            std::mem_fn(&NewChannelGroup::value_type::get) );
       }
    );
-   return streams;
 }
 
 //------ ODDecodeFFmpegTask definitions