SWI-Prolog -- collation

Availability:built-in

collation_key(+Atom, -Key)

Create a Key from Atom for locale-specific comparison. The key is defined such that if the key of atom A precedes the key of atom B in the standard order of terms, A is alphabetically smaller than B using the sort order of the current locale.

The predicate collation_key/2 is used by locale_sort/2 from library(sort). Please examine the implementation of locale_sort/2 as an example of using this call.

The Key is an implementation-defined and generally unreadable string. On systems that do not support locale handling, Key is simply unified with Atom.