Combinations without repeated

Program calculates combinations without repeated elements.

Source: Guide to Prolog Programming (on-line tutorial)

Program source code: combinations_without_repeated.pl

comb2(_,[]).
comb2([X|T],[X|Comb]):-comb2(T,Comb).
comb2([_|T],[X|Comb]):-comb2(T,[X|Comb]).
 
 
% use ?-comb2([1,2,3,4],[X,Y]) to generate combinations with two elements.