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

From cppreference.com
< cpp‎ | numeric‎ | valarray
 
 
 
 
template< class T >

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

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

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

valarray<bool> operator>=( const T& lhsv, const valarray<T>& rhs );
(2)
template< class T >

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

valarray<bool> operator>=( const valarray<T>& lhs, const T& 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.

Contents

[edit] Parameters

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

[edit] Return value

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

[edit] Exceptions

(none)

[edit] 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:

[edit] 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 vector<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