[simd.traits]

# 29 Numerics library [[numerics]](./#numerics)

## 29.10 Data-parallel types [[simd]](simd#traits)

### 29.10.4 Type traits [simd.traits]

[ð](#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)

â *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)

[ð](#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)

[ð](#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)
