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yap-6.3/pl/lists.yap

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:- system_module( '$_lists', [], []).
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:- set_prolog_flag(source, true). % source.
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% memberchk(+Element, +Set)
% means the same thing, but may only be used to test whether a known
% Element occurs in a known Set. In return for this limited use, it
% is more efficient when it is applicable.
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/** @pred memberchk(+ _Element_, + _Set_)
As member/2, but may only be used to test whether a known
_Element_ occurs in a known Set. In return for this limited use, it
is more efficient when it is applicable.
*/
lists:memberchk(X,[X|_]) :- !.
lists:memberchk(X,[_|L]) :-
lists:memberchk(X,L).
% member(?Element, ?Set)
% is true when Set is a list, and Element occurs in it. It may be used
% to test for an element or to enumerate all the elements by backtracking.
% Indeed, it may be used to generate the Set!
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/** @pred member(? _Element_, ? _Set_)
True when _Set_ is a list, and _Element_ occurs in it. It may be used
to test for an element or to enumerate all the elements by backtracking.
*/
lists:member(X,[X|_]).
lists:member(X,[_|L]) :-
lists:member(X,L).
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/** @pred append(? _List1_,? _List2_,? _List3_)
Succeeds when _List3_ unifies with the concatenation of _List1_
and _List2_. The predicate can be used with any instantiation
pattern (even three variables).
*/
lists:append([], L, L).
lists:append([H|T], L, [H|R]) :-
lists:append(T, L, R).
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:- set_prolog_flag(source, false)). % :- no_source.
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% lists:delete(List, Elem, Residue)
% is true when List is a list, in which Elem may or may not occur, and
% Residue is a copy of List with all elements identical to Elem lists:deleted.
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/** @pred delete(+ _List_, ? _Element_, ? _Residue_)
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eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
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True when _List_ is a list, in which _Element_ may or may not
occur, and _Residue_ is a copy of _List_ with all elements
identical to _Element_ deleted.
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eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
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*/
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lists:delete([], _, []).
lists:delete([Head|List], Elem, Residue) :-
Head == Elem, !,
lists:delete(List, Elem, Residue).
lists:delete([Head|List], Elem, [Head|Residue]) :-
lists:delete(List, Elem, Residue).
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:- set_prolog_flag(source, false). % disable source.
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