name = 'conc/3' slug = 'concatenate two lists' description = '''\
conc(L1, L2, L): the list L is obtained by appending the elements of L2 to L1.
conc(L1, L2, L)
L
L2
L1
?- conc([1,2], [3,4], X). X = [1,2,3,4]. ?- conc(X, [], [1,2,3]). X = [1,2,3].