STYLE: Replace NumericTraits<T>::ZeroValue() with T{}

For any type `T` that is supported by `NumericTraits<T>`, the expression
`NumericTraits<T>::ZeroValue()` is just equivalent to `T{}`. `T{}` appears
preferable, because it is more generic, and it may yield faster code than the
corresponding `NumericTraits<T>::ZeroValue()` function call.

Using Notepad++, Replace in Files:

    Find what:
      itk::NumericTraits<(\w+)>::ZeroValue\(\)
      NumericTraits<(\w+)>::ZeroValue\(\)
      itk::NumericTraits<([^ <>]+)>::ZeroValue\(\)
      NumericTraits<([^ <>]+)>::ZeroValue\(\)
      itk::NumericTraits<(typename [^ <>]+)>::ZeroValue\(\)
      NumericTraits<(typename [^ <>]+)>::ZeroValue\(\)
      itk::NumericTraits<(itk::NumericTraits<[^ ]+>::ValueType)>::ZeroValue\(\)
      itk::NumericTraits<(typename itk::NumericTraits<[^ ]+>::ValueType)>::ZeroValue\(\)
      NumericTraits<(typename NumericTraits<[^ ]+>::ValueType)>::ZeroValue\(\)
      itk::NumericTraits<(typename .+)>::ZeroValue\(\)
      NumericTraits<(typename .+)>::ZeroValue\(\)
    Replace with: $1{}
    Filters: itk*.hxx;itk*.h;itk*.cxx
    Directory: ITK\Modules
    [v] Match case
    (*) Regular expression

Excluded "itkNumericTraitsTest.cxx", because it purposely calls
`NumericTraits::ZeroValue()` as part of the test.

Follow-up to pull request #4017
commit 5ac803e
"STYLE: Replace `T var{ NumericTraits<T>::ZeroValue() }` with `T var{}`"

Modules/Core/Common/include/itkBackwardDifferenceOperator.hxx

@@ -29,7 +29,7 @@ BackwardDifferenceOperator<TPixel, TDimension, TAllocator>::GenerateCoefficients
 
   coeff[0] = -1.0 * NumericTraits<PixelType>::OneValue();
   coeff[1] = NumericTraits<PixelType>::OneValue();
-  coeff[2] = NumericTraits<PixelType>::ZeroValue();
+  coeff[2] = PixelType{};
 
   return coeff;
 }

Modules/Core/Common/include/itkBoundingBox.hxx

@@ -134,7 +134,7 @@ BoundingBox<TPointIdentifier, VPointDimension, TCoordRep, TPointsContainer>::Com
   {
     if (this->GetMTime() > m_BoundsMTime)
     {
-      m_Bounds.Fill(NumericTraits<CoordRepType>::ZeroValue());
+      m_Bounds.Fill(CoordRepType{});
       m_BoundsMTime.Modified();
     }
     return false;
@@ -146,7 +146,7 @@ BoundingBox<TPointIdentifier, VPointDimension, TCoordRep, TPointsContainer>::Com
     // start by initializing the values
     if (m_PointsContainer->Size() < 1)
     {
-      m_Bounds.Fill(NumericTraits<CoordRepType>::ZeroValue());
+      m_Bounds.Fill(CoordRepType{});
       m_BoundsMTime.Modified();
       return false;
     }
@@ -285,7 +285,7 @@ auto
 BoundingBox<TPointIdentifier, VPointDimension, TCoordRep, TPointsContainer>::GetDiagonalLength2() const
   -> AccumulateType
 {
-  typename NumericTraits<CoordRepType>::AccumulateType dist2 = NumericTraits<CoordRepType>::ZeroValue();
+  typename NumericTraits<CoordRepType>::AccumulateType dist2 = CoordRepType{};
 
   if (this->ComputeBoundingBox())
   {

Modules/Core/Common/include/itkCellInterface.h

@@ -387,7 +387,7 @@ class ITK_TEMPLATE_EXPORT CellInterface
   CoordRepType
   GetBoundingBoxDiagonalLength2()
   {
-    return NumericTraits<CoordRepType>::ZeroValue();
+    return CoordRepType{};
   }
 
   /** Intersect the given bounding box (bounds[PointDimension*2]) with a line

Modules/Core/Common/include/itkColorTable.hxx

@@ -57,7 +57,7 @@ ColorTable<TComponent>::UseDiscreteColors()
   else
   {
     scale = NumericTraits<TComponent>::OneValue();
-    shift = NumericTraits<TComponent>::ZeroValue();
+    shift = TComponent{};
   }
 
   m_Color[0].Set((TComponent)(0.9 * scale + shift), (TComponent)(shift), (TComponent)(shift));
@@ -123,7 +123,7 @@ ColorTable<TComponent>::UseGrayColors(unsigned int n)
   else
   {
     range = NumericTraits<TComponent>::OneValue();
-    minimum = NumericTraits<TComponent>::ZeroValue();
+    minimum = TComponent{};
   }
   typename NumericTraits<TComponent>::RealType delta;
   if (m_NumberOfColors > 1)
@@ -178,7 +178,7 @@ ColorTable<TComponent>::UseHeatColors(unsigned int n)
   else
   {
     scale = NumericTraits<TComponent>::OneValue();
-    shift = NumericTraits<TComponent>::ZeroValue();
+    shift = TComponent{};
   }
   // Converting from TComponent to RealType may introduce a rounding error, so do static_cast
   constexpr auto max_value_converted =
@@ -238,7 +238,7 @@ ColorTable<TComponent>::UseRandomColors(unsigned int n)
   }
   else
   {
-    minimum = NumericTraits<TComponent>::ZeroValue();
+    minimum = TComponent{};
     maximum = NumericTraits<TComponent>::OneValue();
   }
   for (i = 0; i < n; ++i)

Modules/Core/Common/include/itkCompensatedSummation.hxx

@@ -61,7 +61,7 @@ CompensatedSummationAddElement(TFloat & compensation, TFloat & sum, const TFloat
 template <typename TFloat>
 CompensatedSummation<TFloat>::CompensatedSummation(const TFloat value)
   : m_Sum(value)
-  , m_Compensation(NumericTraits<AccumulateType>::ZeroValue())
+  , m_Compensation(AccumulateType{})
 {}
 
 template <typename TFloat>
@@ -138,16 +138,16 @@ template <typename TFloat>
 void
 CompensatedSummation<TFloat>::ResetToZero()
 {
-  this->m_Sum = NumericTraits<AccumulateType>::ZeroValue();
-  this->m_Compensation = NumericTraits<AccumulateType>::ZeroValue();
+  this->m_Sum = AccumulateType{};
+  this->m_Compensation = AccumulateType{};
 }
 
 template <typename TFloat>
 CompensatedSummation<TFloat> &
 CompensatedSummation<TFloat>::operator=(const FloatType & rhs)
 {
   this->m_Sum = rhs;
-  this->m_Compensation = NumericTraits<AccumulateType>::ZeroValue();
+  this->m_Compensation = AccumulateType{};
 
   return *this;
 }

Modules/Core/Common/include/itkConceptChecking.h

@@ -771,7 +771,7 @@ struct HasZero
     {
       T a;
 
-      a = NumericTraits<T>::ZeroValue();
+      a = T{};
       Detail::IgnoreUnusedVariable(a);
     }
   };

Modules/Core/Common/include/itkCovariantVector.hxx

@@ -101,7 +101,7 @@ template <typename T, unsigned int VVectorDimension>
 typename CovariantVector<T, VVectorDimension>::ValueType CovariantVector<T, VVectorDimension>::operator*(
   const Self & other) const
 {
-  typename NumericTraits<T>::AccumulateType value = NumericTraits<T>::ZeroValue();
+  typename NumericTraits<T>::AccumulateType value = T{};
   for (unsigned int i = 0; i < VVectorDimension; ++i)
   {
     value += (*this)[i] * other[i];
@@ -113,7 +113,7 @@ template <typename T, unsigned int VVectorDimension>
 typename CovariantVector<T, VVectorDimension>::ValueType CovariantVector<T, VVectorDimension>::operator*(
   const Vector<T, VVectorDimension> & other) const
 {
-  typename NumericTraits<T>::AccumulateType value = NumericTraits<T>::ZeroValue();
+  typename NumericTraits<T>::AccumulateType value = T{};
   for (unsigned int i = 0; i < VVectorDimension; ++i)
   {
     value += (*this)[i] * other[i];

Modules/Core/Common/include/itkDiffusionTensor3D.hxx

@@ -115,14 +115,14 @@ DiffusionTensor3D<T>::GetRelativeAnisotropy() const -> RealValueType
   // zero.
   if (trace < NumericTraits<RealValueType>::min())
   {
-    return NumericTraits<RealValueType>::ZeroValue();
+    return RealValueType{};
   }
 
   const RealValueType anisotropy = 3.0 * isp - trace * trace;
 
-  if (anisotropy < NumericTraits<RealValueType>::ZeroValue())
+  if (anisotropy < RealValueType{})
   {
-    return NumericTraits<RealValueType>::ZeroValue();
+    return RealValueType{};
   }
 
   const auto relativeAnisotropySquared = static_cast<RealValueType>(anisotropy / (std::sqrt(3.0) * trace));

Modules/Core/Common/include/itkFloodFilledFunctionConditionalConstIterator.h

@@ -202,7 +202,7 @@ class ITK_TEMPLATE_EXPORT FloodFilledFunctionConditionalConstIterator : public C
 
     this->m_IsAtEnd = true;
     // Initialize the temporary image
-    m_TemporaryPointer->FillBuffer(NumericTraits<typename TTempImage::PixelType>::ZeroValue());
+    m_TemporaryPointer->FillBuffer(typename TTempImage::PixelType{});
 
     for (unsigned int i = 0; i < m_Seeds.size(); ++i)
     {

Modules/Core/Common/include/itkForwardDifferenceOperator.hxx

@@ -28,7 +28,7 @@ ForwardDifferenceOperator<TPixel, VDimension, TAllocator>::GenerateCoefficients(
 {
   CoefficientVector coeff(3);
 
-  coeff[0] = NumericTraits<PixelType>::ZeroValue();
+  coeff[0] = PixelType{};
   coeff[1] = -1.0 * NumericTraits<PixelType>::OneValue();
   coeff[2] = NumericTraits<PixelType>::OneValue();
 

Modules/Core/Common/include/itkHeavisideStepFunction.hxx

@@ -27,16 +27,14 @@ template <typename TInput, typename TOutput>
 auto
 HeavisideStepFunction<TInput, TOutput>::Evaluate(const InputType & input) const -> OutputType
 {
-  return (input >= NumericTraits<InputType>::ZeroValue()) ? NumericTraits<OutputType>::OneValue()
-                                                          : NumericTraits<OutputType>::ZeroValue();
+  return (input >= InputType{}) ? NumericTraits<OutputType>::OneValue() : OutputType{};
 }
 
 template <typename TInput, typename TOutput>
 auto
 HeavisideStepFunction<TInput, TOutput>::EvaluateDerivative(const InputType & input) const -> OutputType
 {
-  return (Math::ExactlyEquals(input, NumericTraits<InputType>::ZeroValue())) ? NumericTraits<OutputType>::OneValue()
-                                                                             : NumericTraits<OutputType>::ZeroValue();
+  return (Math::ExactlyEquals(input, InputType{})) ? NumericTraits<OutputType>::OneValue() : OutputType{};
 }
 
 } // namespace itk

Modules/Core/Common/include/itkMath.h

@@ -577,9 +577,7 @@ struct AlmostEqualsScalarVsComplex
   static bool
   AlmostEqualsFunction(TScalarType scalarVariable, TComplexType complexVariable)
   {
-    if (!AlmostEqualsScalarComparer(
-          complexVariable.imag(),
-          itk::NumericTraits<typename itk::NumericTraits<TComplexType>::ValueType>::ZeroValue()))
+    if (!AlmostEqualsScalarComparer(complexVariable.imag(), typename itk::NumericTraits<TComplexType>::ValueType{}))
     {
       return false;
     }

Modules/Core/Common/include/itkMatrix.h

@@ -276,7 +276,7 @@ class ITK_TEMPLATE_EXPORT Matrix
   inline vnl_matrix_fixed<T, VColumns, VRows>
   GetInverse() const
   {
-    if (vnl_determinant(m_Matrix) == NumericTraits<T>::ZeroValue())
+    if (vnl_determinant(m_Matrix) == T{})
     {
       itkGenericExceptionMacro("Singular matrix. Determinant is 0.");
     }

Modules/Core/Common/include/itkNeighborhoodOperator.h

@@ -170,7 +170,7 @@ class ITK_TEMPLATE_EXPORT NeighborhoodOperator : public Neighborhood<TPixel, VDi
   {
     for (unsigned int i = 0; i < this->Size(); ++i)
     {
-      this->operator[](i) = NumericTraits<PixelType>::ZeroValue();
+      this->operator[](i) = PixelType{};
     }
   }
 

Modules/Core/Common/include/itkNumericTraits.h

@@ -189,7 +189,7 @@ class NumericTraits : public std::numeric_limits<T>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
   /** Return the length of the scalar. This API is needed for
    * VariableLengthVector because
@@ -368,7 +368,7 @@ class NumericTraits<bool> : public std::numeric_limits<bool>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -474,7 +474,7 @@ class NumericTraits<char> : public std::numeric_limits<char>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -596,7 +596,7 @@ class NumericTraits<signed char> : public std::numeric_limits<signed char>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -700,7 +700,7 @@ class NumericTraits<unsigned char> : public std::numeric_limits<unsigned char>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -802,7 +802,7 @@ class NumericTraits<short> : public std::numeric_limits<short>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -905,7 +905,7 @@ class NumericTraits<unsigned short> : public std::numeric_limits<unsigned short>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -1007,7 +1007,7 @@ class NumericTraits<int> : public std::numeric_limits<int>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -1129,7 +1129,7 @@ class NumericTraits<unsigned int> : public std::numeric_limits<unsigned int>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -1232,7 +1232,7 @@ class NumericTraits<long> : public std::numeric_limits<long>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -1335,7 +1335,7 @@ class NumericTraits<unsigned long> : public std::numeric_limits<unsigned long>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -1439,7 +1439,7 @@ class NumericTraits<float> : public std::numeric_limits<float>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -1542,7 +1542,7 @@ class NumericTraits<double> : public std::numeric_limits<double>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -1653,7 +1653,7 @@ class NumericTraits<long double> : public std::numeric_limits<long double>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -1757,7 +1757,7 @@ class NumericTraits<long long> : public std::numeric_limits<long long>
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -1852,7 +1852,7 @@ class NumericTraits<unsigned long long> : public std::numeric_limits<unsigned lo
     {
       itkGenericExceptionMacro("Cannot set the size of a scalar to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 };
 
@@ -1978,7 +1978,7 @@ class NumericTraits<std::complex<TComponent>>
     {
       itkGenericExceptionMacro("Cannot set the size of a complex to " << s);
     }
-    m = NumericTraits<ValueType>::ZeroValue();
+    m = ValueType{};
   }
 
 #if defined(ITK_LEGACY_REMOVE)

Modules/Core/Common/include/itkNumericTraitsArrayPixel.h

@@ -91,7 +91,7 @@ class NumericTraits<Array<T>>
   {
     Self b(a.Size());
 
-    b.Fill(NumericTraits<T>::ZeroValue());
+    b.Fill(T{});
     return b;
   }
 
@@ -121,7 +121,7 @@ class NumericTraits<Array<T>>
   SetLength(Array<T> & m, const unsigned int s)
   {
     m.SetSize(s);
-    m.Fill(NumericTraits<T>::ZeroValue());
+    m.Fill(T{});
   }
 
   /** Get the length of the input array. */