NAME¶

std::list::sort - std::list::sort

Synopsis¶

void sort(); (1)
template< class Compare > (2)
void sort( Compare comp );

Sorts the elements and preserves the order of equivalent elements. No references or
iterators become invalidated.

1) Elements are compared using operator<.
2) Elements are compared using comp.

If an exception is thrown, the order of elements in *this is unspecified.

Parameters¶

comparison function object (i.e. an object that satisfies the requirements of
Compare) which returns true if the first argument is less than (i.e. is
ordered before) the second.

The signature of the comparison function should be equivalent to the
following:

bool cmp(const Type1& a, const Type2& b);
comp -
While the signature does not need to have const&, the function must not
modify the objects passed to it and must be able to accept all values of type
(possibly const) Type1 and Type2 regardless of value category (thus, Type1&
is not allowed
, nor is Type1 unless for Type1 a move is equivalent to a copy
(since C++11)).
The types Type1 and Type2 must be such that an object of type
list<T,Allocator>::const_iterator can be dereferenced and then implicitly
converted to both of them.

Type requirements¶

-
Compare must meet the requirements of Compare.

Return value¶

(none)

Complexity¶

Given \(\scriptsize N\)N as size():

1) Approximately \(\scriptsize N \cdot log(N)\)N·log(N) comparisons using operator<.
2) Approximately \(\scriptsize N \cdot log(N)\)N·log(N) applications of the
comparison function comp.

Notes¶

std::sort requires random access iterators and so cannot be used with list. This
function also differs from std::sort in that it does not require the element type of
the list to be swappable, preserves the values of all iterators, and performs a
stable sort.

Example¶

// Run this code

#include <functional>
#include <iostream>
#include <list>

std::ostream& operator<<(std::ostream& ostr, const std::list<int>& list)
{
for (const int i : list)
ostr << ' ' << i;
return ostr;
}

int main()
{
std::list<int> list{8, 7, 5, 9, 0, 1, 3, 2, 6, 4};
std::cout << "initially: " << list << '\n';

list.sort();
std::cout << "ascending: " << list << '\n';

list.sort(std::greater<int>());
std::cout << "descending:" << list << '\n';
}

Output:¶

initially: 8 7 5 9 0 1 3 2 6 4
ascending: 0 1 2 3 4 5 6 7 8 9
descending: 9 8 7 6 5 4 3 2 1 0

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 1207 C++98 it was unclear whether iterators and/or keep valid
references will be invalidated

See also¶

reverse reverses the order of the elements
(public member function)