Merge pull request #5671 from N-Dekker/GetLength-constexpr

STYLE: Make `NumericTraits::GetLength` constexpr whenever possible

Author: hjmjohnson

Modules/Core/Common/include/itkNumericTraits.h

@@ -198,14 +198,14 @@ class NumericTraits : public std::numeric_limits<T>
    * VariableLengthVector will provide a different implementation
    * where a vector of the correct size is built.
    */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const T &)
   {
     return GetLength();
   }
 
   /** Return the length of the scalar: 1. Array types can return a different value */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return 1;

Modules/Core/Common/include/itkNumericTraitsCovariantVectorPixel.h

@@ -161,14 +161,14 @@ class NumericTraits<CovariantVector<T, D>>
   }
 
   /** Return the length of the vector. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const CovariantVector<T, D> &)
   {
     return D;
   }
 
   /** Return the length of the vector. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return D;

Modules/Core/Common/include/itkNumericTraitsDiffusionTensor3DPixel.h

@@ -163,14 +163,14 @@ class NumericTraits<DiffusionTensor3D<T>>
   }
 
   /** Return the size of the tensor. Always returns 6. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const DiffusionTensor3D<T> &)
   {
     return 6;
   }
 
   /** Return the size of the tensor. Always returns 6. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return 6;

Modules/Core/Common/include/itkNumericTraitsFixedArrayPixel.h

@@ -157,14 +157,14 @@ class NumericTraits<FixedArray<T, D>>
   }
 
   /** Return the length of the array. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const FixedArray<T, D> &)
   {
     return D;
   }
 
   /** Return the length of the array. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return D;

Modules/Core/Common/include/itkNumericTraitsPointPixel.h

@@ -148,14 +148,14 @@ class NumericTraits<Point<T, D>>
   }
 
   /** Return the dimensionality of the point. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const Point<T, D> &)
   {
     return D;
   }
 
   /** Return the dimensionality of the point. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return D;

Modules/Core/Common/include/itkNumericTraitsRGBAPixel.h

@@ -188,14 +188,14 @@ class NumericTraits<RGBAPixel<T>>
   }
 
   /** Return the dimensionality of the pixel. Always returns 4. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const RGBAPixel<T> &)
   {
     return 4;
   }
 
   /** Return the dimensionality of the pixel. Always returns 4. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return 4;

Modules/Core/Common/include/itkNumericTraitsRGBPixel.h

@@ -188,14 +188,14 @@ class NumericTraits<RGBPixel<T>>
   }
 
   /** Return the dimensionality of the pixel. Always returns 3. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const RGBPixel<T> &)
   {
     return 3;
   }
 
   /** Return the dimensionality of the pixel. Always returns 3. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return 3;

Modules/Core/Common/include/itkNumericTraitsTensorPixel.h

@@ -163,14 +163,14 @@ class NumericTraits<SymmetricSecondRankTensor<T, D>>
   }
 
   /** Return the size of the underlying FixedArray. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const SymmetricSecondRankTensor<T, D> &)
   {
     return GetLength();
   }
 
   /** Return the size of the underlying FixedArray. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return D * (D + 1) / 2;

Modules/Core/Common/include/itkNumericTraitsVectorPixel.h

@@ -203,14 +203,14 @@ class NumericTraits<Vector<T, D>>
   }
 
   /** Return the size of the vector. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const Vector<T, D> &)
   {
     return D;
   }
 
   /** Return the size of the vector. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return D;