std::valarray

Defined in header `<valarray>`
template< class T > class valarray;

std::valarray is the class for representing and manipulating arrays of values. It supports element-wise mathematical operations and various forms of generalized subscript operators, slicing and indirect access.

Template parameters

the type of the elements. The type must meet the NumericType requirements

Member types

Member type	Definition
`value_type`	`T`
`iterator`(C++11)	unspecified mutable iterator type, meeting the LegacyRandomAccessIterator requirements and the LegacyContiguousIterator requirements(until C++20)and modeling `contiguous_iterator`(since C++20), such that `std::iterator_traits<iterator>::value_type` is `T`, and `std::iterator_traits<iterator>::reference` is T&
`const_iterator`(C++11)	unspecified constant iterator type, meeting the LegacyRandomAccessIterator requirements and the LegacyContiguousIterator requirements(until C++20)and modeling `contiguous_iterator`(since C++20), such that `std::iterator_traits<const_iterator>::value_type` is `T`, and `std::iterator_traits<const_iterator>::reference` is constT&

Member functions

(constructor)	constructs new numeric array (public member function)
(destructor)	destructs the numeric array (public member function)
operator=	assigns the contents (public member function)
operator[]	get/set valarray element, slice, or mask (public member function)
operator+operator-operator~operator!	applies a unary arithmetic operator to each element of the valarray (public member function)
operator+=operator-=operator*=operator/=operator%=operator&=operator\|=operator^=operator<<=operator>>=	applies compound assignment operator to each element of the valarray (public member function)
swap	swaps with another valarray (public member function)
size	returns the size of valarray (public member function)
resize	changes the size of valarray (public member function)
sum	calculates the sum of all elements (public member function)
min	returns the smallest element (public member function)
max	returns the largest element (public member function)
shift	zero-filling shift the elements of the valarray (public member function)
cshift	circular shift of the elements of the valarray (public member function)
apply	applies a function to every element of a valarray (public member function)
begin (C++11)	obtains the beginning iterator of `valarray` (public member function)
end (C++11)	obtains the past-the-end iterator of `valarray` (public member function)

Non-member functions

std::swap(std::valarray) (C++11)	specializes the `std::swap` algorithm (function template)
operator+operator-operator*operator/operator%operator&operator\|operator^operator<<operator>>operator&&operator	applies binary operators to each element of two valarrays, or a valarray and a value (function template)
operator==operator!=operator<operator<=operator>operator>=	compares two valarrays or a valarray with a value (function template)
abs(std::valarray)	applies the function `abs` to each element of valarray (function template)
Exponential functions
exp(std::valarray)	applies the function `std::exp` to each element of valarray (function template)
log(std::valarray)	applies the function `std::log` to each element of valarray (function template)
log10(std::valarray)	applies the function `std::log10` to each element of valarray (function template)
Power functions
pow(std::valarray)	applies the function `std::pow` to two valarrays or a valarray and a value (function template)
sqrt(std::valarray)	applies the function `std::sqrt` to each element of valarray (function template)
Trigonometric functions
sin(std::valarray)	applies the function `std::sin` to each element of valarray (function template)
cos(std::valarray)	applies the function `std::cos` to each element of valarray (function template)
tan(std::valarray)	applies the function `std::tan` to each element of valarray (function template)
asin(std::valarray)	applies the function `std::asin` to each element of valarray (function template)
acos(std::valarray)	applies the function `std::acos` to each element of valarray (function template)
atan(std::valarray)	applies the function `std::atan` to each element of valarray (function template)
atan2(std::valarray)	applies the function `std::atan2` to a valarray and a value (function template)
Hyperbolic functions
sinh(std::valarray)	applies the function `std::sinh` to each element of valarray (function template)
cosh(std::valarray)	applies the function `std::cosh` to each element of valarray (function template)
tanh(std::valarray)	applies the function `std::tanh` to each element of valarray (function template)

Helper classes

slice	BLAS-like slice of a valarray: starting index, length, stride (class)
slice_array	proxy to a subset of a valarray after applying a slice (class template)
gslice	generalized slice of a valarray: starting index, set of lengths, set of strides (class)
gslice_array	proxy to a subset of a valarray after applying a gslice (class template)
mask_array	proxy to a subset of a valarray after applying a boolean mask `operator[]` (class template)
indirect_array	proxy to a subset of a valarray after applying indirect `operator[]` (class template)

Deduction guides(since C++17)

Notes

std::valarray and helper classes are defined to be free of certain forms of aliasing, thus allowing operations on these classes to be optimized similar to the effect of the keyword restrict in the C programming language. In addition, functions and operators that take valarray arguments are allowed to return proxy objects to make it possible for the compiler to optimize an expression such as v1 = a * v2 + v3; as a single loop that executes v1[i] = a * v2[i] + v3[i]; avoiding any temporaries or multiple passes. However, expression templates make the same optimization technique available for any C++ container, and the majority of numeric libraries prefer expression templates to valarrays for flexibility. Some C++ standard library implementations use expression templates to implement efficient operations on std::valarray (e.g. GNU libstdc++ and LLVM libc++). Only rarely are valarrays optimized any further, as in e.g. Intel Integrated Performance Primitives.

Feature-test macro	Value	Std	Feature
`__cpp_lib_valarray`	`202511L`	(C++26) (DR11)	`begin` and `end` member functions, and `iterator` and `const_iterator` member types of `std::valarray`^[1]

As of 2026-05-27, libstdc++ has not treated the modifications of begin and end functions from P3016R6 as a defect report against C++11, and only applies the changes since C++26.

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
P3016R6	C++11	1) `valarray` lacked member types `iterator` and `const_iterator` 2) `valarray` had inconsistent non-member `begin()` and `end()` functions	1) member types added 2) changed to member functions

simd::basic_vec (C++26)	data-parallel vector type (class template)
simd::vec (C++26)	convenience alias template for `basic_vec` that can specify its width (alias template)
simd::basic_mask (C++26)	data-parallel type with the element type bool (class template)
simd::mask (C++26)	convenience alias template for `basic_mask` that can specify its width (alias template)

std::valarray

Template parameters

Member types

Member functions

Non-member functions

Exponential functions

Power functions

Trigonometric functions

Hyperbolic functions

Helper classes

Deduction guides(since C++17)

Notes

Defect reports

See also