From aa2adb72225efba8750b27e42e24de34c1f6a841 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20Vondru=C5=A1?= <mosra@centrum.cz>
Date: Fri, 24 May 2019 19:53:15 +0200
Subject: [PATCH] Math: add IsScalar, IsVector, IsIntegral and IsFloatingPoint
 type traits.

The standard ones are not good enough, so let's roll out my own.
---
 doc/changelog.dox                       |   2 +
 src/Magnum/Math/Test/TypeTraitsTest.cpp |  61 ++++++++++
 src/Magnum/Math/TypeTraits.h            | 150 +++++++++++++++++++++++-
 3 files changed, 210 insertions(+), 3 deletions(-)

diff --git a/doc/changelog.dox b/doc/changelog.dox
index 4afa89964..1381e7914 100644
--- a/doc/changelog.dox
+++ b/doc/changelog.dox
@@ -123,6 +123,8 @@ See also:
     @ref Corrade::Utility::Debug::color modifier
 -   Added convenience @ref BoolVector2, @ref BoolVector3 and @ref BoolVector4
     typedefs to the root namespace
+-   New @ref Math::IsScalar, @ref Math::IsVector, @ref Math::IsIntegral and
+    @ref Math::IsFloatingPoint type traits
 
 @subsubsection changelog-latest-new-platform Platform libraries
 
diff --git a/src/Magnum/Math/Test/TypeTraitsTest.cpp b/src/Magnum/Math/Test/TypeTraitsTest.cpp
index c4f860733..13590906c 100644
--- a/src/Magnum/Math/Test/TypeTraitsTest.cpp
+++ b/src/Magnum/Math/Test/TypeTraitsTest.cpp
@@ -27,6 +27,7 @@
 #include <Corrade/TestSuite/Tester.h>
 #include <Corrade/Utility/DebugStl.h>
 
+#include "Magnum/Math/Math.h"
 #include "Magnum/Math/TypeTraits.h"
 #include "Magnum/Math/Constants.h"
 
@@ -38,6 +39,11 @@ struct TypeTraitsTest: Corrade::TestSuite::Tester {
     void sizeOfLongDouble();
     void name();
 
+    void isScalar();
+    void isVector();
+    void isIntegral();
+    void isFloatingPoint();
+
     template<class T> void equalsIntegral();
     template<class T> void equalsFloatingPoint0();
     template<class T> void equalsFloatingPoint1();
@@ -95,6 +101,11 @@ TypeTraitsTest::TypeTraitsTest() {
     addTests({&TypeTraitsTest::sizeOfLongDouble,
               &TypeTraitsTest::name,
 
+              &TypeTraitsTest::isScalar,
+              &TypeTraitsTest::isVector,
+              &TypeTraitsTest::isIntegral,
+              &TypeTraitsTest::isFloatingPoint,
+
               &TypeTraitsTest::equalsIntegral<UnsignedByte>,
               &TypeTraitsTest::equalsIntegral<Byte>,
               &TypeTraitsTest::equalsIntegral<UnsignedShort>,
@@ -166,6 +177,56 @@ void TypeTraitsTest::name() {
     CORRADE_COMPARE(TypeTraits<Float>::name(), std::string{"Float"});
 }
 
+void TypeTraitsTest::isScalar() {
+    CORRADE_VERIFY(IsScalar<char>::value);
+    CORRADE_VERIFY(IsScalar<UnsignedShort>::value);
+    CORRADE_VERIFY(IsScalar<Deg<Float>>::value);
+    CORRADE_VERIFY((IsScalar<Unit<Rad, Double>>::value));
+    CORRADE_VERIFY(!IsScalar<Vector2<Float>>::value);
+    CORRADE_VERIFY(!IsVector<Matrix2x3<Float>>::value);
+    CORRADE_VERIFY(!IsScalar<char*>::value);
+    CORRADE_VERIFY(!IsScalar<bool>::value);
+}
+
+void TypeTraitsTest::isVector() {
+    CORRADE_VERIFY(!IsVector<UnsignedByte>::value);
+    CORRADE_VERIFY(!IsVector<Deg<UnsignedByte>>::value);
+    CORRADE_VERIFY((IsVector<Vector<2, Deg<Float>>>::value));
+    CORRADE_VERIFY(IsVector<Color3<UnsignedByte>>::value);
+    CORRADE_VERIFY(!IsVector<Matrix2x3<Float>>::value);
+    CORRADE_VERIFY(!IsVector<char*>::value);
+}
+
+void TypeTraitsTest::isIntegral() {
+    /* These three are usually different types */
+    CORRADE_VERIFY(IsIntegral<char>::value);
+    CORRADE_VERIFY(IsIntegral<Byte>::value);
+    CORRADE_VERIFY(IsIntegral<UnsignedByte>::value);
+
+    CORRADE_VERIFY(IsIntegral<Int>::value);
+    CORRADE_VERIFY((IsIntegral<Vector<7, UnsignedInt>>::value));
+    #ifndef CORRADE_TARGET_EMSCRIPTEN
+    CORRADE_VERIFY(IsIntegral<Vector2<Long>>::value);
+    #endif
+    CORRADE_VERIFY(!IsIntegral<Deg<Float>>::value);
+    CORRADE_VERIFY(!IsIntegral<char*>::value);
+    CORRADE_VERIFY(!IsIntegral<bool>::value);
+}
+
+void TypeTraitsTest::isFloatingPoint() {
+    CORRADE_VERIFY(!IsFloatingPoint<Int>::value);
+    CORRADE_VERIFY(!(IsFloatingPoint<Vector<7, UnsignedInt>>::value));
+    CORRADE_VERIFY(IsFloatingPoint<Double>::value);
+    CORRADE_VERIFY((IsFloatingPoint<Vector<2, Float>>::value));
+    #ifndef CORRADE_TARGET_EMSCRIPTEN
+    CORRADE_VERIFY(IsFloatingPoint<Vector2<long double>>::value);
+    #endif
+    CORRADE_VERIFY(IsFloatingPoint<Deg<Float>>::value);
+    CORRADE_VERIFY((IsFloatingPoint<Unit<Rad, Float>>::value));
+    CORRADE_VERIFY(!IsFloatingPoint<Deg<Half>>::value);
+    CORRADE_VERIFY(!IsFloatingPoint<char*>::value);
+}
+
 template<class T> void TypeTraitsTest::equalsIntegral() {
     setTestCaseName(std::string{"equalsIntegral<"} + TypeTraits<T>::name() + ">");
 
diff --git a/src/Magnum/Math/TypeTraits.h b/src/Magnum/Math/TypeTraits.h
index 044119439..fedf02357 100644
--- a/src/Magnum/Math/TypeTraits.h
+++ b/src/Magnum/Math/TypeTraits.h
@@ -26,11 +26,12 @@
 */
 
 /** @file
- * @brief Class @ref Magnum::Math::TypeTraits
+ * @brief Type traits
  */
 
 #include <Corrade/Utility/StlMath.h>
 
+#include "Magnum/Math/Math.h"
 #include "Magnum/Types.h"
 
 /**
@@ -74,6 +75,148 @@ for more headroom.
 
 namespace Magnum { namespace Math {
 
+/**
+@brief Whether @p T is an arithmetic scalar type
+
+Equivalent to @ref std::true_type for all builtin scalar integer and
+floating-point types and in addition also @ref Deg and @ref Rad; equivalent to
+@ref std::false_type otherwise. The @ref Half type deliberately doesn't support
+any arithmetic, so it's not treated as a scalar type.
+
+Note that this is *different* from @ref std::is_scalar, which is @cpp true @ce
+also for enums or pointers --- it's rather closer to @ref std::is_arithmetic,
+except that it doesn't give @ref std::true_type for @cpp bool @ce. The name is
+chosen particularly for the @ref IsVector / @ref IsScalar distinction.
+@see @ref IsFloatingPoint, @ref IsIntegral
+*/
+template<class T> struct IsScalar
+    #ifndef DOXYGEN_GENERATING_OUTPUT
+    : std::false_type
+    #endif
+    {};
+
+#ifndef DOXYGEN_GENERATING_OUTPUT
+/* Can't use our own typedefs because they don't cover all types (signed char
+   vs char, long vs long long etc.). Funny that char != signed char but signed
+   int = int */
+template<> struct IsScalar<char>: std::true_type {};
+template<> struct IsScalar<signed char>: std::true_type {};
+template<> struct IsScalar<unsigned char>: std::true_type {};
+template<> struct IsScalar<short>: std::true_type {};
+template<> struct IsScalar<unsigned short>: std::true_type {};
+template<> struct IsScalar<int>: std::true_type {};
+template<> struct IsScalar<unsigned int>: std::true_type {};
+template<> struct IsScalar<long>: std::true_type {};
+template<> struct IsScalar<unsigned long>: std::true_type {};
+template<> struct IsScalar<long long>: std::true_type {};
+template<> struct IsScalar<unsigned long long>: std::true_type {};
+template<> struct IsScalar<float>: std::true_type {};
+template<> struct IsScalar<double>: std::true_type {};
+#ifndef CORRADE_TARGET_EMSCRIPTEN
+template<> struct IsScalar<long double>: std::true_type {};
+#endif
+template<template<class> class Derived, class T> struct IsScalar<Unit<Derived, T>>: std::true_type {};
+template<class T> struct IsScalar<Deg<T>>: std::true_type {};
+template<class T> struct IsScalar<Rad<T>>: std::true_type {};
+#endif
+
+/**
+@brief Whether @p T is an arithmetic vector type
+
+Equivalent to @ref std::true_type for all @ref Vector types and their
+subclasses; equivalent to @ref std::false_type otherwise. In particular, gives
+@ref std::false_type for @ref BoolVector, all matrix types, @ref Complex or
+@ref Quaternion.
+@see @ref IsScalar, @ref IsFloatingPoint, @ref IsIntegral
+*/
+template<class T> struct IsVector
+    #ifndef DOXYGEN_GENERATING_OUTPUT
+    : std::false_type
+    #endif
+    {};
+
+#ifndef DOXYGEN_GENERATING_OUTPUT
+template<std::size_t size, class T> struct IsVector<Vector<size, T>>: std::true_type {};
+template<class T> struct IsVector<Vector2<T>>: std::true_type {};
+template<class T> struct IsVector<Vector3<T>>: std::true_type {};
+template<class T> struct IsVector<Vector4<T>>: std::true_type {};
+template<class T> struct IsVector<Color3<T>>: std::true_type {};
+template<class T> struct IsVector<Color4<T>>: std::true_type {};
+#endif
+
+/**
+@brief Whether @p T is integral
+
+Equivalent to @ref std::true_type for all integral scalar and vector types
+supported by Magnum math; equivalent to @ref std::false_type otherwise.
+
+Unlike @ref std::is_integral this is @ref std::false_type for @cpp bool @ce.
+@see @ref IsFloatingPoint, @ref IsScalar, @ref IsVector
+*/
+template<class T> struct IsIntegral
+    #ifndef DOXYGEN_GENERATING_OUTPUT
+    : std::false_type
+    #endif
+    {};
+
+#ifndef DOXYGEN_GENERATING_OUTPUT
+/* Can't use our own typedefs because they don't cover all types (signed char
+   vs char, long vs long long etc.). Funny that char != signed char but signed
+   int = int */
+template<> struct IsIntegral<char>: std::true_type {};
+template<> struct IsIntegral<signed char>: std::true_type {};
+template<> struct IsIntegral<unsigned char>: std::true_type {};
+template<> struct IsIntegral<short>: std::true_type {};
+template<> struct IsIntegral<unsigned short>: std::true_type {};
+template<> struct IsIntegral<int>: std::true_type {};
+template<> struct IsIntegral<unsigned int>: std::true_type {};
+template<> struct IsIntegral<long>: std::true_type {};
+template<> struct IsIntegral<unsigned long>: std::true_type {};
+template<> struct IsIntegral<long long>: std::true_type {};
+template<> struct IsIntegral<unsigned long long>: std::true_type {};
+template<std::size_t size, class T> struct IsIntegral<Vector<size, T>>: IsIntegral<T> {};
+template<class T> struct IsIntegral<Vector2<T>>: IsIntegral<T> {};
+template<class T> struct IsIntegral<Vector3<T>>: IsIntegral<T> {};
+template<class T> struct IsIntegral<Vector4<T>>: IsIntegral<T> {};
+template<class T> struct IsIntegral<Color3<T>>: IsIntegral<T> {};
+template<class T> struct IsIntegral<Color4<T>>: IsIntegral<T> {};
+/* I don't expect Deg/Rad to ever have an integral base type */
+#endif
+
+/**
+@brief Whether @p T is floating-point
+
+Equivalent to @ref std::true_type for all floating-point scalar and vector
+types supported by Magnum math including @ref Deg and @ref Rad; equivalent to
+@ref std::false_type otherwise. The @ref Half type deliberately doesn't support
+any arithmetic, so it's not treated as a floating-point type.
+@see @ref IsIntegral, @ref IsScalar, @ref IsVector, @ref std::is_floating_point
+*/
+template<class T> struct IsFloatingPoint
+    #ifndef DOXYGEN_GENERATING_OUTPUT
+    : std::false_type
+    #endif
+    {};
+
+#ifndef DOXYGEN_GENERATING_OUTPUT
+template<> struct IsFloatingPoint<Float>: std::true_type {};
+template<> struct IsFloatingPoint<Double>: std::true_type {};
+#ifndef CORRADE_TARGET_EMSCRIPTEN
+template<> struct IsFloatingPoint<long double>: std::true_type {};
+#endif
+template<std::size_t size, class T> struct IsFloatingPoint<Vector<size, T>>: IsFloatingPoint<T> {};
+template<class T> struct IsFloatingPoint<Vector2<T>>: IsFloatingPoint<T> {};
+template<class T> struct IsFloatingPoint<Vector3<T>>: IsFloatingPoint<T> {};
+template<class T> struct IsFloatingPoint<Vector4<T>>: IsFloatingPoint<T> {};
+template<class T> struct IsFloatingPoint<Color3<T>>: IsFloatingPoint<T> {};
+template<class T> struct IsFloatingPoint<Color4<T>>: IsFloatingPoint<T> {};
+/* Deg<Half> is legal but Half is not an arithmetic type (and thus not
+   floating-point), so need to check the underlying type as well */
+template<template<class> class Derived, class T> struct IsFloatingPoint<Unit<Derived, T>>: IsFloatingPoint<T> {};
+template<class T> struct IsFloatingPoint<Deg<T>>: IsFloatingPoint<T> {};
+template<class T> struct IsFloatingPoint<Rad<T>>: IsFloatingPoint<T> {};
+#endif
+
 namespace Implementation {
     template<class T> struct TypeTraitsDefault {
         TypeTraitsDefault() = delete;
@@ -89,11 +232,12 @@ namespace Implementation {
 }
 
 /**
-@brief Traits class for numeric types
+@brief Traits class for builtin arithmetic types
 
 Traits classes are usable for detecting type features at compile time without
 the need for repeated code such as method overloading or template
-specialization for given types.
+specialization for given types. All builtin arithmetic types have this class
+implemented.
 */
 template<class T> struct TypeTraits: Implementation::TypeTraitsDefault<T> {
     /*