SWI-Prolog -- partition/5

Availability::- use_module(library(apply)).(can be autoloaded)

[semidet]partition(:Pred, +List, ?Less, ?Equal, ?Greater)

Filter List according to Pred in three sets. For each element Xi of List, its destination is determined by call(Pred, Xi, Place), where Place must be unified to one of <, = or >. Pred must be deterministic.