sort(3pm) Perl Programmers Reference Guide sort(3pm)
NAME
sort - perl pragma to control sort() behaviour
SYNOPSIS
The sort pragma is now a no-op, and its use is discouraged. These three
operations are valid, but have no effect:
use sort 'stable'; # guarantee stability
use sort 'defaults'; # revert to default behavior
no sort 'stable'; # stability not important
DESCRIPTION
Historically the "sort" pragma you can control the behaviour of the
builtin sort() function.
Prior to v5.28.0 there were two other options:
use sort '_mergesort';
use sort '_qsort'; # or '_quicksort'
If you try and specify either of these in v5.28+ it will croak.
The default sort has been stable since v5.8.0, and given this
consistent behaviour for almost two decades, everyone has come to
assume stability.
Stability will remain the default - hence there is no need for a pragma
for code to opt into stability "just in case" this changes - it won't.
We do not foresee going back to offering multiple implementations of
general purpose sorting - hence there is no future need to offer a
pragma to choose between them.
If you know that you care that much about performance of your sorting,
and that for your use case and your data, it was worth investigating
alternatives, possible to identify an alternative from our default that
was better, and the cost of switching was worth it, then you know more
than we do. Likely whatever choices we can give are not as good as
implementing your own. (For example, a Radix sort can be faster than
O(n log n), but can't be used for all keys and has larger overheads.)
We are not averse to changing the sort algorithm, but we don't see the
benefit in offering the choice of two general purpose implementations.
CAVEATS
The function sort::current() was provided to report the current state
of the sort pragmata. This function was not exported, and there is no
code to call it on CPAN. It is now deprecated, and will warn by
default.
As we no longer store any sort "state", it can no longer return the
correct value, so it will always return the string "stable", as this is
consistent with what we actually have implemented.
perl v5.38.2 2023-11-28 sort(3pm)
perl 5.38.2 - Generated Mon Dec 16 15:33:51 CST 2024