10.18 Rem's Algorithm—library(rem)

This library module maintains equivalence classes using Rem's algorithm. Exported predicates:

rem_create(+Size, -REM)

creates an equivalence representation function REM which maps each of the nodes 1..Size to itself.

rem_head(?Node, +REM, -Head)

is true when Head is the representative of the equivalence class that Node belongs to in the given REM.

rem_equivalent(?Node1, ?Node2, +REM)

is true when Node1 and Node2 belong to the same equivalence class in the given REM.

rem_add_link(?Node1, ?Node2, +OldREM, -NewREM)

is true when adding the equivalence Node1===Node2 to the partition represented by OldREM yields a partition which is represented by NewREM. If Node1 or Node2 is uninstantiated, it will backtrack over all the nodes. It's not clear how useful this is.