Porting to other Prolog Systems:

Sicstus Prolog:

lean runs without changes.

Quintus Prolog:

lean runs without changes.

SWI-Prolog:

Required changes in leantest.pl, as suggested by M. E. Gegundez Arias (gegundez@mizar.us.es):

Eclipse:

Required changes, as suggested by Reiner Haehnle (reiner@mail.informatik.kit.edu)