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pl:prolog:pllib:list_intersection [2019/06/27 15:50] |
pl:prolog:pllib:list_intersection [2019/06/27 15:50] (aktualna) |
| ====== List intersection ====== |
| {{tag>lists}} |
| ===== Description ===== |
| Finding the intersection of two lists. |
| |
| **Source**: The Art of Prolog |
| ===== Download ===== |
| Program source code: {{list_intersection.pl}} |
| ===== Listing ===== |
| <code prolog> |
| /* |
| intersection(Xs,Ys,Is) :- Is is the intersection of the elements in Xs and Ys. |
| */ |
| |
| intersection([X|Xs],Ys,[X|Is]) :- member(X,Ys), intersection(Xs,Ys,Is). |
| intersection([X|Xs],Ys,Is) :- nonmember(X,Ys), intersection(Xs,Ys,Is). |
| intersection([],Ys,[]). |
| /* |
| nonmember(X,Xs) :- X is not a member of the list Xs. |
| */ |
| nonmember(X,[Y|Ys]) :- X \== Y, nonmember(X,Ys). |
| nonmember(X,[]). |
| |
| % Program 13.2 Finding the intersection of two lists |
| </code> |
| ===== Comments ===== |
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