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

Header: <valarray>

Compares each value within the numeric array with another value.

# Declarations

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 );

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 );

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 );

# 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.

# Notes

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

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

# Example

#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';
}

# Defect reports

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