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cppdraft/simd/traits.md

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+[simd.traits]
+
+# 29 Numerics library [[numerics]](./#numerics)
+
+## 29.10 Data-parallel types [[simd]](simd#traits)
+
+### 29.10.4 Type traits [simd.traits]
+
+[🔗](#lib:alignment,simd)
+
+`template<class T, class U = typename T::value_type> struct alignment { see below };
+`
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L17146)
+
+alignment<T, U> has a member value if and only if
+
+- [(1.1)](#1.1)
+
+T is a specialization of basic_mask and U is bool, or
+
+- [(1.2)](#1.2)
+
+T is a specialization of basic_vec and U is a
+ vectorizable type[.](#1.sentence-1)
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L17157)
+
+If value is present, the type alignment<T, U> is aBinaryTypeTrait with a base characteristic ofintegral_constant<size_t, N> for some unspecifiedN ([[simd.ctor]](simd.ctor "29.10.7.2 basic_­vec constructors"), [[simd.loadstore]](simd.loadstore "29.10.8.6 basic_­vec load and store functions"))[.](#2.sentence-1)
+
+[*Note [1](#note-1)*:
+
+value identifies the alignment restrictions on pointers used for
+(converting) loads and stores for the given type T on arrays of typeU[.](#2.sentence-2)
+
+— *end note*]
+
+[3](#3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L17168)
+
+The behavior of a program that adds specializations for alignment is undefined[.](#3.sentence-1)
+
+[🔗](#lib:rebind,simd)
+
+`template<class T, class V> struct rebind { using type = see below; };
+`
+
+[4](#4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L17179)
+
+The member type is present if and only if
+
+- [(4.1)](#4.1)
+
+V is a data-parallel type,
+
+- [(4.2)](#4.2)
+
+T is a vectorizable type, and
+
+- [(4.3)](#4.3)
+
+*deduce-abi-t*<T, V​::​size()> has a member type type[.](#4.sentence-1)
+
+[5](#5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L17188)
+
+If V is a specialization of basic_vec, let Abi1 denote
+an ABI tag such that basic_vec<T, Abi1>​::​​size() equalsV​::​size()[.](#5.sentence-1)
+
+If V is a specialization of basic_mask, let Abi1 denote an ABI tag such that basic_mask<sizeof(T),
+Abi1>​::​​size() equals V​::​size()[.](#5.sentence-2)
+
+[6](#6)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L17196)
+
+Where present, the member typedef type names basic_vec<T, Abi1> if V is a specialization of basic_vec orbasic_mask<sizeof(T), Abi1> if V is a specialization ofbasic_mask[.](#6.sentence-1)
+
+[🔗](#lib:resize,simd)
+
+`template<simd-size-type N, class V> struct resize { using type = see below; };
+`
+
+[7](#7)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L17209)
+
+Let T denote
+
+- [(7.1)](#7.1)
+
+typename V​::​value_type if V is a specialization of basic_vec,
+
+- [(7.2)](#7.2)
+
+otherwise *integer-from*<*mask-element-size*<V>> if V is a specialization of basic_mask[.](#7.sentence-1)
+
+[8](#8)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L17220)
+
+The member type is present if and only if
+
+- [(8.1)](#8.1)
+
+V is a data-parallel type, and
+
+- [(8.2)](#8.2)
+
+*deduce-abi-t*<T, N> has a member type type[.](#8.sentence-1)
+
+[9](#9)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L17227)
+
+If V is a specialization of basic_vec, let Abi1 denote an
+ABI tag such that basic_vec<T, Abi1>​::​​size() equals N[.](#9.sentence-1)
+
+If V is a specialization of basic_mask, let Abi1 denote an ABI tag such that basic_mask<sizeof(T), Abi1>​::​size() equals N[.](#9.sentence-2)
+
+[10](#10)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L17233)
+
+Where present, the member typedef type names basic_vec<T, Abi1> if V is a specialization of basic_vec orbasic_mask<sizeof(T), Abi1> if V is a specialization ofbasic_mask[.](#10.sentence-1)