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meta.h
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1 //
2 // Copyright 2023 Pixar
3 //
4 // Licensed under the Apache License, Version 2.0 (the "Apache License")
5 // with the following modification; you may not use this file except in
6 // compliance with the Apache License and the following modification to it:
7 // Section 6. Trademarks. is deleted and replaced with:
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9 // 6. Trademarks. This License does not grant permission to use the trade
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14 // You may obtain a copy of the Apache License at
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24 
25 #ifndef PXR_BASE_TF_META_H
26 #define PXR_BASE_TF_META_H
27 
28 #include "pxr/pxr.h"
29 
30 #include <cstddef>
31 #include <tuple>
32 #include <type_traits>
33 
34 // Some small metaprogramming utilities.
35 
37 
38 // Simple compile-time type list.
39 template <class... Args> struct TfMetaList {};
40 
41 // Helper for TfMetaApply.
42 template<template <class...> class Cls, class List>
44 
45 template<template <class...> class Cls, class... Args>
46 struct Tf_MetaApplyImpl<Cls, TfMetaList<Args...>>
47 {
48  using Type = Cls<Args...>;
49 };
50 
51 // Apply \p TypeList<Args...> to class template \p Cls, producing Cls<Args...>
52 template <template <class...> class Cls, class TypeList>
54 
55 // TfMetaHead<A1, A2, ... An> -> A1
56 template <class Head, class...>
57 using TfMetaHead = Head;
58 
59 // TfMetaTail<A1, A2, ... An> -> TfMetaList<A2, ... An>.
60 template <class Head, class... Tail>
61 using TfMetaTail = TfMetaList<Tail...>;
62 
63 // TfMetaDecay<A1, A2, ... An> ->
64 // TfMetaList<std::decay_t<A1>, ... std::decay_t<An>>
65 template <class... Ts>
67 
68 // TfMetaLength produces an integral_constant<size_t, N> where N is the number
69 // of \p Xs.
70 template <class... Xs>
71 using TfMetaLength = std::integral_constant<size_t, sizeof...(Xs)>;
72 
74 
75 #endif // PXR_BASE_TF_META_H
std::integral_constant< size_t, sizeof...(Xs)> TfMetaLength
Definition: meta.h:71
PXR_NAMESPACE_CLOSE_SCOPE PXR_NAMESPACE_OPEN_SCOPE
Definition: path.h:1432
#define PXR_NAMESPACE_CLOSE_SCOPE
Definition: pxr.h:91
Head TfMetaHead
Definition: meta.h:57
typename Tf_MetaApplyImpl< Cls, TypeList >::Type TfMetaApply
Definition: meta.h:53