STYLE: Prefer C++11 type alias over typedef

== http://en.cppreference.com/w/cpp/language/type_alias ==

Type alias is a name that refers to a previously defined type (similar
to typedef).

A type alias declaration introduces a name which can be used as a
synonym for the type denoted by type-id. It does not introduce a new
type and it cannot change the meaning of an existing type name. There is
no difference between a type alias declaration and typedef declaration.
This declaration may appear in block scope, class scope, or namespace
scope.

== https://www.quora.com/Is-using-typedef-in-C++-considered-a-bad-practice ==

While typedef is still available for backward compatibility, the new
Type Alias syntax 'using Alias = ExistingLongName;' is more consistent
with the flow of C++ than the old typedef syntax 'typedef
ExistingLongName Alias;', and it also works for templates (Type alias,
alias template (since C++11)), so leftover 'typedef' aliases will differ
in style from any alias templates.

======= First pass regex manual changes ==================
cat > /tmp/typdef_vim_script.vim << EOF
:%s/typedef  *\(.*<\_s*.*[>,]\_s*.*[><,]\_s*.*[><,]\_s*.*[><,]\_s*.*[><,]\_s*.*[^>]>\)\_s *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge
:%s/typedef  *\(.*<\_s*.*[><,]\_s*.*[><,]\_s*.*[><,]\_s*.*[><,]\_s*.*[^>]>\)\_s *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge
:%s/typedef  *\(.*<\_s*.*[><,]\_s*.*[><,]\_s*.*[><,]\_s*.*[^>]>\)\_s *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge
:%s/typedef  *\(.*<\_s*.*[><,]\_s*.*[><,]\_s*.*[^>]>\)\_s *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge
:%s/typedef  *\(.*<\_s*.*[><,]\_s*.*[^>]>\)\_s *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge
:%s/typedef  *\(.*<\_s*.*[^>]>\)\_s *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge

:%s/\*\(.*\) typedef\(s*\)\(.*\)\*/*\1 type alias\3*/ge
:%s/\*\*\(.*\) typedef\(s*\)\(.*\)/**\1 type alias\3/ge
:%s/\/\/\(.*\)typedefs/\/\/\1type alias/ge

:%s/typedef  *\(.*<\_s*.*,\_s*.*,\_s*[^>]*>\)  *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge
:%s/\/\/\(.*\)typedefs/\/\/\1type alias/ge
:%s/typedef  *\(.*<\_s*.*[>,]\_s.*[^>]>\)\_s *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge
:%s/\*\(.*\) typedef\(s*\)\(.*\)\*/*\1 type alias\3*/ge
:%s/\*\*\(.*\) typedef\(s*\)\(.*\)/**\1 type alias\3/ge
:%s/typedef  *\(.*[><,]*\_s*.*[><,]\_s.*[^>]>\)\_s *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge
:%s/typedef  *\(.*<\_s*.*[>,]\_s*.*[><,]\_s*.*[><,]\_s*.*[^>]>\)\_s *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge
:%s/typedef  *\(.*<\_s*.*[>,]\_s*.*[><,]\_s*.*[><,]\_s*.*[><,]\_s*.*[><,]\_s*.*[^>]>\)\_s *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge

:%s/typedef  *\(.*\) * \([a-zA-Z0-9]*\);/using \2 = \1;/g
:%s/typedef  *\(.*<\_s*.*,\n[^>]*>\)  *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge
:%s/typedef  *\(.*<\_s*.*,.*>\{-}>\)  *\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/using \2 = \1;/ge
:%s/\(  *\)typedef  *\(.*<.*>\)\_s\(  *\)\([A-Za-z0-9][A-Za-z0-9]*\);\{-};/\1using \4 =\r\1    \2;/ge
:%s/typedef support\(\.*\)/type alias support/ge

:%s/  *;/;/ge
:w
:q
EOF

for ff in $(git grep -l "typedef" |fgrep -v ThirdParty |head -n 1500); do
   vim -S /tmp/typdef_vim_script.vim $ff;
done

clang-tidy -header-filter=.* \
     -checks=-*,modernize-use-using \
     -fix -p=~/Dashboard/src/ITK-clangtidy \
     $(git grep -l typedef |fgrep -v ThirdParty|fgrep "cxx")

Change-Id: I7d121a71b220e74337ec7626c6b4f53b61c64c53

Author: hjmjohnson

Documentation/Doxygen/NeighborhoodIterators.dox

@@ -65,9 +65,9 @@ have been omitted for clarity. )
 
 
 \code
-1   typedef itk::Image<float, 2> ImageType;
-2   typedef itk::SmartNeighborhoodIterator<ImageType> NeighborhoodIterator;
-3   typedef itk::ImageRegionIterator<ImageType>       ImageIterator;
+1   using ImageType = itk::Image<float, 2>;
+2   using NeighborhoodIterator = itk::SmartNeighborhoodIterator<ImageType>;
+3   using ImageIterator = itk::ImageRegionIterator<ImageType>;
 4
 5   ImageType::Pointer input_image  = GetImageSomehow();
 6   ImageType::Pointer output_image = GetImageSomehow();
@@ -98,7 +98,7 @@ Note that the computational work is confined to lines 18-26. The code is also
 completely generalized for multiple dimensions.  For example, changing line 1
 to:
 \code
-1   typedef itk::Image<float, 5> ImageType;
+1   using ImageType = itk::Image<float, 5>;
 \endcode
 produces an averaging filter for five-dimensional images. 
 
@@ -185,7 +185,7 @@ Rewriting the inner product code using this approach looks like the following.
 omitting some template parameters for simplicity.)
 
 \code
-typedef NeighborhoodAlgorithm::ImageBoundaryFacesCalculator RegionFinderType;
+using RegionFinderType = NeighborhoodAlgorithm::ImageBoundaryFacesCalculator;
 
 LaPlacianOperator<double, InputImageType::ImageDimension> OP;
 

Examples/DataRepresentation/Containers/TreeContainer.cxx

@@ -63,8 +63,8 @@ int main(int, char* [])
 
 
   // Software Guide : BeginCodeSnippet
-  typedef int                          NodeType;
-  typedef itk::TreeContainer<NodeType> TreeType;
+  using NodeType = int;
+  using TreeType = itk::TreeContainer<NodeType>;
   TreeType::Pointer tree = TreeType::New();
   // Software Guide : EndCodeSnippet
 
@@ -262,8 +262,8 @@ int main(int, char* [])
 
 
   // Software Guide : BeginCodeSnippet
-  typedef itk::TreeIteratorBase<TreeType>      IteratorType;
-  typedef itk::TreeIteratorClone<IteratorType> IteratorCloneType;
+  using IteratorType = itk::TreeIteratorBase<TreeType>;
+  using IteratorCloneType = itk::TreeIteratorClone<IteratorType>;
   IteratorCloneType anotherChildItClone = childIt;
   // Software Guide : EndCodeSnippet
 

Examples/DataRepresentation/Image/Image1.cxx

@@ -45,7 +45,7 @@ int main(int, char *[])
   // Software Guide : EndLatex
   //
   // Software Guide : BeginCodeSnippet
-  typedef itk::Image< unsigned short, 3 > ImageType;
+  using ImageType = itk::Image< unsigned short, 3 >;
   // Software Guide : EndCodeSnippet
 
 

Examples/DataRepresentation/Image/Image2.cxx

@@ -39,10 +39,10 @@ int main( int , char * argv[])
   // Software Guide : EndLatex
 
   // Software Guide : BeginCodeSnippet
-  typedef unsigned char          PixelType;
+  using PixelType = unsigned char;
   const unsigned int             Dimension = 3;
 
-  typedef itk::Image< PixelType, Dimension >   ImageType;
+  using ImageType = itk::Image< PixelType, Dimension >;
   // Software Guide : EndCodeSnippet
 
   // Software Guide : BeginLatex
@@ -64,7 +64,7 @@ int main( int , char * argv[])
   // Software Guide : EndLatex
 
   // Software Guide : BeginCodeSnippet
-  typedef itk::ImageFileReader< ImageType >  ReaderType;
+  using ReaderType = itk::ImageFileReader< ImageType >;
   // Software Guide : EndCodeSnippet
 
   // Software Guide : BeginLatex

Examples/DataRepresentation/Image/Image3.cxx

@@ -36,7 +36,7 @@
 int main(int, char *[])
 {
   // First the image type should be declared
-  typedef itk::Image< unsigned short, 3 > ImageType;
+  using ImageType = itk::Image< unsigned short, 3 >;
 
   // Then the image object can be created
   ImageType::Pointer image = ImageType::New();

Examples/DataRepresentation/Image/Image4.cxx

@@ -79,7 +79,7 @@ static itk::Image< unsigned short, 3 >::IndexType GetIndexFromMouseClick()
 int main(int, char *[])
 {
   const unsigned int Dimension=3;
-  typedef itk::Image< unsigned short, Dimension > ImageType;
+  using ImageType = itk::Image< unsigned short, Dimension >;
   ImageType::Pointer image = ImageType::New();
 
   const ImageType::SizeType  size  = {{ 200, 200, 200}}; //Size along {X,Y,Z}
@@ -255,7 +255,7 @@ int main(int, char *[])
   // Software Guide : EndLatex
 
   // Software Guide : BeginCodeSnippet
-  typedef itk::Point< double, ImageType::ImageDimension > PointType;
+  using PointType = itk::Point< double, ImageType::ImageDimension >;
   // Software Guide : EndCodeSnippet
 
   // Software Guide : BeginLatex
@@ -383,7 +383,7 @@ int main(int, char *[])
   // SoftwareGuide : EndLatex
 
   // Software Guide : BeginCodeSnippet
-  typedef itk::Matrix<double, Dimension, Dimension> MatrixType;
+  using MatrixType = itk::Matrix<double, Dimension, Dimension>;
   MatrixType SpacingMatrix;
   SpacingMatrix.Fill( 0.0F );
 
@@ -396,7 +396,7 @@ int main(int, char *[])
     image->GetDirection();
   const ImageType::PointType &ImageOrigin = image->GetOrigin();
 
-  typedef itk::Vector< double, Dimension > VectorType;
+  using VectorType = itk::Vector< double, Dimension >;
   VectorType LeftEyeIndexVector;
   LeftEyeIndexVector[0]= LeftEyeIndex[0];
   LeftEyeIndexVector[1]= LeftEyeIndex[1];

Examples/DataRepresentation/Image/Image5.cxx

@@ -63,10 +63,10 @@ int main(int argc, char * argv[])
   // Software Guide : EndLatex
 
   // Software Guide : BeginCodeSnippet
-  typedef unsigned char   PixelType;
+  using PixelType = unsigned char;
   const unsigned int Dimension = 3;
 
-  typedef itk::Image< PixelType, Dimension > ImageType;
+  using ImageType = itk::Image< PixelType, Dimension >;
   // Software Guide : EndCodeSnippet
 
   // Software Guide : BeginLatex
@@ -79,7 +79,7 @@ int main(int argc, char * argv[])
   // Software Guide : EndLatex
 
   // Software Guide : BeginCodeSnippet
-  typedef itk::ImportImageFilter< PixelType, Dimension >   ImportFilterType;
+  using ImportFilterType = itk::ImportImageFilter< PixelType, Dimension >;
   // Software Guide : EndCodeSnippet
 
   // Software Guide : BeginLatex
@@ -237,7 +237,7 @@ int main(int argc, char * argv[])
   // Software Guide : EndLatex
 
   // Software Guide : BeginCodeSnippet
-  typedef itk::ImageFileWriter< ImageType > WriterType;
+  using WriterType = itk::ImageFileWriter< ImageType >;
   WriterType::Pointer writer = WriterType::New();
 
   writer->SetFileName( argv[1] );

Examples/DataRepresentation/Image/ImageAdaptor1.cxx

@@ -59,8 +59,8 @@
 class CastPixelAccessor
 {
 public:
-  typedef unsigned char InternalType;
-  typedef float         ExternalType;
+  using InternalType = unsigned char;
+  using ExternalType = float;
 
   static void Set(InternalType & output, const ExternalType & input)
     {
@@ -102,11 +102,11 @@ int main( int argc, char *argv[] )
 
 
 // Software Guide : BeginCodeSnippet
-  typedef unsigned char  InputPixelType;
+  using InputPixelType = unsigned char;
   const   unsigned int   Dimension = 2;
-  typedef itk::Image< InputPixelType, Dimension >   ImageType;
+  using ImageType = itk::Image< InputPixelType, Dimension >;
 
-  typedef itk::ImageAdaptor< ImageType, CastPixelAccessor > ImageAdaptorType;
+  using ImageAdaptorType = itk::ImageAdaptor< ImageType, CastPixelAccessor >;
   ImageAdaptorType::Pointer adaptor = ImageAdaptorType::New();
 // Software Guide : EndCodeSnippet
 
@@ -119,7 +119,7 @@ int main( int argc, char *argv[] )
 
 
 // Software Guide : BeginCodeSnippet
-  typedef itk::ImageFileReader< ImageType >   ReaderType;
+  using ReaderType = itk::ImageFileReader< ImageType >;
   ReaderType::Pointer reader = ReaderType::New();
 // Software Guide : EndCodeSnippet
 
@@ -151,7 +151,7 @@ int main( int argc, char *argv[] )
 
 
 // Software Guide : BeginCodeSnippet
-  typedef itk::ImageRegionIteratorWithIndex< ImageAdaptorType >  IteratorType;
+  using IteratorType = itk::ImageRegionIteratorWithIndex< ImageAdaptorType >;
   IteratorType  it( adaptor, adaptor->GetBufferedRegion() );
 
   double sum = 0.0;

Examples/DataRepresentation/Image/ImageAdaptor2.cxx

@@ -52,8 +52,8 @@
 class RedChannelPixelAccessor
 {
 public:
-  typedef itk::RGBPixel<float>   InternalType;
-  typedef               float    ExternalType;
+  using InternalType = itk::RGBPixel<float>;
+  using ExternalType = float;
 
   static ExternalType Get( const InternalType & input )
     {
@@ -100,12 +100,12 @@ int main( int argc, char *argv[] )
 
 
   // Software Guide : BeginCodeSnippet
-  typedef RedChannelPixelAccessor::InternalType  InputPixelType;
+  using InputPixelType = RedChannelPixelAccessor::InternalType;
   const   unsigned int   Dimension = 2;
-  typedef itk::Image< InputPixelType, Dimension >   ImageType;
+  using ImageType = itk::Image< InputPixelType, Dimension >;
 
-  typedef itk::ImageAdaptor<  ImageType,
-                              RedChannelPixelAccessor > ImageAdaptorType;
+  using ImageAdaptorType = itk::ImageAdaptor<  ImageType,
+                              RedChannelPixelAccessor >;
 
   ImageAdaptorType::Pointer adaptor = ImageAdaptorType::New();
   // Software Guide : EndCodeSnippet
@@ -120,7 +120,7 @@ int main( int argc, char *argv[] )
 
 
   // Software Guide : BeginCodeSnippet
-  typedef itk::ImageFileReader< ImageType >   ReaderType;
+  using ReaderType = itk::ImageFileReader< ImageType >;
   ReaderType::Pointer reader = ReaderType::New();
   // Software Guide : EndCodeSnippet
 
@@ -144,13 +144,13 @@ int main( int argc, char *argv[] )
 
 
   // Software Guide : BeginCodeSnippet
-  typedef itk::Image< unsigned char, Dimension >   OutputImageType;
-  typedef itk::RescaleIntensityImageFilter< ImageAdaptorType,
-                                            OutputImageType
-                                               >   RescalerType;
+  using OutputImageType = itk::Image< unsigned char, Dimension >;
+  using RescalerType = itk::RescaleIntensityImageFilter<
+                                            ImageAdaptorType,
+                                            OutputImageType >;
 
   RescalerType::Pointer rescaler = RescalerType::New();
-  typedef itk::ImageFileWriter< OutputImageType >   WriterType;
+  using WriterType = itk::ImageFileWriter< OutputImageType >;
   WriterType::Pointer writer = WriterType::New();
   // Software Guide : EndCodeSnippet
 
@@ -213,8 +213,8 @@ int main( int argc, char *argv[] )
   class GreenChannelPixelAccessor
   {
   public:
-    typedef itk::RGBPixel<float>   InternalType;
-    typedef               float    ExternalType;
+    using InternalType = itk::RGBPixel<float>;
+    using ExternalType = float;
 
     static ExternalType Get( const InternalType & input )
       {
@@ -237,8 +237,8 @@ int main( int argc, char *argv[] )
   class BlueChannelPixelAccessor
     {
   public:
-    typedef itk::RGBPixel<float>   InternalType;
-    typedef               float    ExternalType;
+    using InternalType = itk::RGBPixel<float>;
+    using ExternalType = float;
 
     static ExternalType Get( const InternalType & input )
       {

Examples/DataRepresentation/Image/ImageAdaptor3.cxx

@@ -66,8 +66,8 @@ namespace itk
 class VectorPixelAccessor
 {
 public:
-  typedef itk::CovariantVector<float,2>   InternalType;
-  typedef                      float      ExternalType;
+  using InternalType = itk::CovariantVector<float,2>;
+  using ExternalType = float;
 
   VectorPixelAccessor() : m_Index(0) {}
 
@@ -130,13 +130,13 @@ int main( int argc, char *argv[] )
 
 
 // Software Guide : BeginCodeSnippet
-  typedef unsigned char  InputPixelType;
+  using InputPixelType = unsigned char;
   const   unsigned int   Dimension = 2;
-  typedef itk::Image< InputPixelType,  Dimension  >   InputImageType;
-  typedef itk::CovariantVector< float, Dimension  >   VectorPixelType;
-  typedef itk::Image< VectorPixelType, Dimension  >   VectorImageType;
-  typedef itk::GradientRecursiveGaussianImageFilter< InputImageType,
-                                        VectorImageType> GradientFilterType;
+  using InputImageType = itk::Image< InputPixelType,  Dimension  >;
+  using VectorPixelType = itk::CovariantVector< float, Dimension  >;
+  using VectorImageType = itk::Image< VectorPixelType, Dimension  >;
+  using GradientFilterType = itk::GradientRecursiveGaussianImageFilter< InputImageType,
+                                        VectorImageType>;
 
   GradientFilterType::Pointer gradient = GradientFilterType::New();
 // Software Guide : EndCodeSnippet
@@ -151,8 +151,8 @@ int main( int argc, char *argv[] )
 //  Software Guide : EndLatex
 
 // Software Guide : BeginCodeSnippet
-  typedef itk::ImageAdaptor<  VectorImageType,
-                              itk::VectorPixelAccessor > ImageAdaptorType;
+  using ImageAdaptorType = itk::ImageAdaptor<  VectorImageType,
+                              itk::VectorPixelAccessor >;
 
   ImageAdaptorType::Pointer adaptor = ImageAdaptorType::New();
 // Software Guide : EndCodeSnippet
@@ -184,7 +184,7 @@ int main( int argc, char *argv[] )
 
 
 // Software Guide : BeginCodeSnippet
-  typedef itk::ImageFileReader< InputImageType >   ReaderType;
+  using ReaderType = itk::ImageFileReader< InputImageType >;
   ReaderType::Pointer reader = ReaderType::New();
   gradient->SetInput( reader->GetOutput() );
 
@@ -207,11 +207,11 @@ int main( int argc, char *argv[] )
 // Software Guide : EndCodeSnippet
 
 
-  typedef itk::Image< unsigned char, Dimension >   OutputImageType;
-  typedef itk::RescaleIntensityImageFilter< ImageAdaptorType, OutputImageType>
-    RescalerType;
+  using OutputImageType = itk::Image< unsigned char, Dimension >;
+  using RescalerType = itk::RescaleIntensityImageFilter< ImageAdaptorType,
+                                                         OutputImageType>;
   RescalerType::Pointer rescaler = RescalerType::New();
-  typedef itk::ImageFileWriter< OutputImageType >   WriterType;
+  using WriterType = itk::ImageFileWriter< OutputImageType >;
   WriterType::Pointer writer = WriterType::New();
 
   writer->SetFileName( argv[2] );