function template
<forward_list>

std::relational operators (forward_list)

(1)
template <class T, class Alloc>
  bool operator== (const forward_list<T,Alloc>& lhs, const forward_list<T,Alloc>& rhs);
(2)
template <class T, class Alloc>
  bool operator!= (const forward_list<T,Alloc>& lhs, const forward_list<T,Alloc>& rhs);
(3)
template <class T, class Alloc>
  bool operator<  (const forward_list<T,Alloc>& lhs, const forward_list<T,Alloc>& rhs);
(4)
template <class T, class Alloc>
  bool operator<= (const forward_list<T,Alloc>& lhs, const forward_list<T,Alloc>& rhs);
(5)
template <class T, class Alloc>
  bool operator>  (const forward_list<T,Alloc>& lhs, const forward_list<T,Alloc>& rhs);
(6)
template <class T, class Alloc>
  bool operator>= (const forward_list<T,Alloc>& lhs, const forward_list<T,Alloc>& rhs);
Relational operators for forward_list
Performs the appropriate comparison operation between the forward_list containers lhs and rhs.

Operations == and != are performed by first comparing the sizes (i.e., the distance between begin and end), and if they match, the elements are compared sequentially using algorithm equal, which stops at the first mismatch.

Operations <, >, <= and >= behave as if using algorithm lexicographical_compare, which compares the elements sequentially using operator< reflexively, stopping at the first mismatch.

These operators are overloaded in header <forward_list>.

Parameters

lhs, rhs
forward_list containers (to the left- and right-hand side of the operator, respectively), having both the same template parameters (T and Alloc).

Example

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// forward_list comparisons
#include <iostream>
#include <forward_list>

int main ()
{
  std::forward_list<int> a = {10, 20, 30};
  std::forward_list<int> b = {10, 20, 30};
  std::forward_list<int> c = {30, 20, 10};

  if (a==b) std::cout << "a and b are equal\n";
  if (b!=c) std::cout << "b and c are not equal\n";
  if (b<c) std::cout << "b is less than c\n";
  if (c>b) std::cout << "c is greater than b\n";
  if (a<=b) std::cout << "a is less than or equal to b\n";
  if (a>=b) std::cout << "a is greater than or equal to b\n";

  return 0;
}


Output:
a and b are equal
b and c are not equal
b is less than c
c is greater than b
a is less than or equal to b
a is greater than or equal to b

Return Value

true if the condition holds, and false otherwise.

Complexity

Linear in both lhs and rhs's sizes.

Iterator validity

No changes.

Data races

Both containers, lhs and rhs, are accessed.
Up to all of their contained elements may be accessed.

Exception safety

If the type of the elements supports the appropriate operation with no-throw guarantee, the function never throws exceptions (no-throw guarantee).
In any case, the function cannot modify its arguments.

See also