% * -*- Mode: Prolog -*- */ % Database of species mammal(mouse). mammal(human). sp(zebrafish). sp(X) :- mammal(X). % rule for generating a pair of (non-identical) species (asymmetric) pair(X,Y) :- sp(X),sp(Y),X@ $@'. '$X-$Y.pair' <-- ['$X.single', '$Y.single'], ['cat $X.single $Y.single > $@', 'echo Files: $X.single $Y.single >> $@'].