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intersection/3

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This commit is contained in:
Vítor Santos Costa II 2010-04-21 00:15:11 +01:00
parent 2566ebcee5
commit b0b42d0e31
2 changed files with 19 additions and 2 deletions
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9
docs/yap.tex
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@ -4149,7 +4149,7 @@ The following predicates provide counting:
@cnindex plus/3 @cnindex plus/3
True if @var{Int3} = @var{Int1} + @var{Int2}. At least two of the True if @var{Int3} = @var{Int1} + @var{Int2}. At least two of the
three arguments must be instantiated to integers. three arguments must be instantiated to integers.
@end table
@node I/O, Database, Arithmetic, Top @node I/O, Database, Arithmetic, Top
@section I/O Predicates @section I/O Predicates
@ -9006,6 +9006,13 @@ If @var{Low} and @var{High} are integers with @var{Low} =<
@var{High}, unify @var{List} to a list @code{[Low, Low+1, ...High]}. See @var{High}, unify @var{List} to a list @code{[Low, Low+1, ...High]}. See
also @code{between/3}. also @code{between/3}.
@item intersection(+@var{Set1}, +@var{Set2}, +@var{Set3})
@findex intersection/3
@syindex intersection/3
@cnindex intersection/3
Succeeds if @var{Set3} unifies with the intersection of @var{Set1} and
@var{Set2}. @var{Set1} and @var{Set2} are lists without duplicates. They
need not be ordered.
@end table @end table
@node LineUtilities, MapList, Lists, Library @node LineUtilities, MapList, Lists, Library

12
library/lists.yap
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@ -35,7 +35,8 @@
flatten/2, flatten/2,
max_list/2, max_list/2,
min_list/2, min_list/2,
numlist/3 numlist/3,
intersection/3
]). ]).
:- use_module(library(error), :- use_module(library(error),
@ -390,3 +391,12 @@ numlist_(L, U, [L|Ns]) :-
numlist_(L2, U, Ns). numlist_(L2, U, Ns).
% copied from SWI lists library.
intersection([], _, []) :- !.
intersection([X|T], L, Intersect) :-
memberchk(X, L), !,
Intersect = [X|R],
intersection(T, L, R).
intersection([_|T], L, R) :-
intersection(T, L, R).