operator==,!=,<,<=,>,>= (std::valarray)

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Defined in header <valarray>
template < class T >

std:: valarray < bool > operator == ( const std:: valarray < T > & lhs, const std:: valarray < T > & rhs ) ;
template < class T >
std:: valarray < bool > operator ! = ( const std:: valarray < T > & lhs, const std:: valarray < T > & rhs ) ;
template < class T >
std:: valarray < bool > operator < ( const std:: valarray < T > & lhs, const std:: valarray < T > & rhs ) ;
template < class T >
std:: valarray < bool > operator <= ( const std:: valarray < T > & lhs, const std:: valarray < T > & rhs ) ;
template < class T >
std:: valarray < bool > operator > ( const std:: valarray < T > & lhs, const std:: valarray < T > & rhs ) ;
template < class T >

std:: valarray < bool > operator >= ( const std:: valarray < T > & lhs, const std:: valarray < T > & rhs ) ;
(1)
template < class T >

std:: valarray < bool > operator == ( const typename std:: valarray < T > :: value_type & lhsv,
const std:: valarray < T > & rhs ) ;
template < class T >
std:: valarray < bool > operator ! = ( const typename std:: valarray < T > :: value_type & lhsv,
const std:: valarray < T > & rhs ) ;
template < class T >
std:: valarray < bool > operator < ( const typename std:: valarray < T > :: value_type & lhsv,
const std:: valarray < T > & rhs ) ;
template < class T >
std:: valarray < bool > operator <= ( const typename std:: valarray < T > :: value_type & lhsv,
const std:: valarray < T > & rhs ) ;
template < class T >
std:: valarray < bool > operator > ( const typename std:: valarray < T > :: value_type & lhsv,
const std:: valarray < T > & rhs ) ;
template < class T >
std:: valarray < bool > operator >= ( const typename std:: valarray < T > :: value_type & lhsv,

const std:: valarray < T > & rhs ) ;
(2)
template < class T >

std:: valarray < bool > operator == ( const std:: valarray < T > & lhs,
const typename std:: valarray < T > :: value_type & rhsv ) ;
template < class T >
std:: valarray < bool > operator ! = ( const std:: valarray < T > & lhs,
const typename std:: valarray < T > :: value_type & rhsv ) ;
template < class T >
std:: valarray < bool > operator < ( const std:: valarray < T > & lhs,
const typename std:: valarray < T > :: value_type & rhsv ) ;
template < class T >
std:: valarray < bool > operator <= ( const std:: valarray < T > & lhs,
const typename std:: valarray < T > :: value_type & rhsv ) ;
template < class T >
std:: valarray < bool > operator > ( const std:: valarray < T > & lhs,
const typename std:: valarray < T > :: value_type & rhsv ) ;
template < class T >
std:: valarray < bool > operator >= ( const std:: valarray < T > & lhs,

const typename std:: valarray < T > :: value_type & rhsv ) ;
(3)

Compares each value within the numeric array with another value.

1) Returns a numeric array of bool containing elements each of which is obtained by applying the indicated comparison operator to the corresponding values of lhs and rhs .

The behavior is undefined if size ( ) ! = v. size ( ) .

2) Returns a numeric array of bool containing elements each of which is obtained by applying the indicated comparison operator to lhsv and the corresponding value of rhs .
3) Returns a numeric array of bool containing elements each of which is obtained by applying the indicated comparison operator to the corresponding value of lhs and rhsv .

Parameters

lhs, rhs - numeric arrays to compare
lhsv, rhsv - values to compare to each element within a numeric array

Return value

A numeric array of bool containing comparison results of corresponding elements.

Exceptions

May throw implementation-defined exceptions.

Notes

Each of the operators can only be instantiated if the following requirements are met:

  • The indicated operator can be applied to type T .
  • The result value can be unambiguously converted to bool .

The function can be implemented with the return type different from std::valarray . In this case, the replacement type has the following properties:

Example

Run this code 
#include <iostream>
#include <valarray>
 
int main()
{
    // zero all negatives in a valarray
    std::valarray<int> v = {1, -1, 0, -3, 10, -1, -2};
    std::cout << "Before: ";
    for (auto n : v)
        std::cout << n << ' ';
    std::cout << '\n';
    v[v < 0] = 0;
    std::cout << "After: ";
    for (auto n : v)
        std::cout << n << ' ';
    std::cout << '\n';
 
    // convert the valarray<bool> result of == to a single bool
    std::valarray<int> a = {1, 2, 3};
    std::valarray<int> b = {2, 4, 6};
 
    std::cout << "2*a == b is " << std::boolalpha
              << (2 * a == b).min() << '\n';
}

Output: 

Before: 1 -1 0 -3 10 -1 -2
After: 1 0 0 0 10 0 0
2*a == b is true

Defect reports

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

DR Applied to Behavior as published Correct behavior
LWG 3074 C++98 T is deduced from both the scalar and the valarray for (2,3) ,
disallowing mixed-type calls 		only deduce T from the valarray
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