Module pairs
:- use_module(library(pairs)).Reasoning about pairs.
Pairs are Prolog terms with principal functor (-)/2. A pair often has the form Key-Value. The predicates of this library relate pairs to keys and values.
pairs_keys_values(?Pairs, ?Keys, ?Values)
The first argument is a list of Pairs, the second the corresponding Keys, and the third argument the corresponding values.
pairs_keys(?Pairs, ?Keys)
Same as pairs_keys_values(Pairs, Keys, _).
pairs_values(?Pairs, ?Values)
Same as pairs_keys_values(Pairs, _, Values).