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103 lines
2.3 KiB
Mathematica
103 lines
2.3 KiB
Mathematica
%---------------------------------------------------------------------------%
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% vim: ts=4 sw=4 et ft=mercury
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%---------------------------------------------------------------------------%
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:- module myset.
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:- interface.
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:- import_module list.
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:- import_module io.
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:- type set(T).
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% convert list to set
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:- func set(list(T)) = set(T).
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% convert set to list
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:- pred set_to_list(set(T)::in, list(T)::out) is cc_multi.
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:- func set_to_sorted_list(set(T)) = list(T).
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% empty set
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:- func {} = set(T).
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:- pred is_empty(set(T)::in) is semidet.
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% singleton set
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:- func {T} = set(T).
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% union of two sets
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:- func set(T) + set(T) = set(T).
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:- mode in + in = out is det.
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% union of an element and a set
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:- func [T | set(T)] = set(T).
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% :- mode [in | in] = out is det.
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:- mode [out | out] = in is cc_nondet.
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:- pred print_myset_rep(set(T)::in, io::di, io::uo) is cc_multi.
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:- implementation.
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:- import_module bool.
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:- import_module require.
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:- type set(T)
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---> set_rep(list(T))
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where equality is set_equal.
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:- pred set_equal(set(T)::in, set(T)::in) is semidet.
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set_equal(Set1, Set2) :-
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set_to_sorted_list(Set1) = set_to_sorted_list(Set2).
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set(List) = set_rep(List).
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set_to_list(set_rep(List), List).
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set_to_sorted_list(Set) =
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promise_only_solution(
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( pred(Sorted::out) is cc_multi :-
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Set = set_rep(Unsorted),
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list.sort(Unsorted, Sorted)
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)
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).
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{} = set_rep([]).
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{X} = set_rep([X]).
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is_empty(Set) :-
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promise_only_solution(
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( pred(Empty::out) is cc_multi :-
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Set = set_rep(List),
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Empty = (if List = [] then yes else no)
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)
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) = yes.
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Set1 + Set2 =
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promise_only_solution(
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( pred(Union::out) is cc_multi :-
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Set1 = set_rep(List1),
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Set2 = set_rep(List2),
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list.append(List1, List2, UnionList),
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Union = set_rep(UnionList)
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)
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).
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% [Element | set_rep(Rest)] = set_rep([Element | Rest]).
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[Element | set_rep(Rest)] = UnionSet :-
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( if is_empty(UnionSet) then
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fail
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else
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UnionSet = set_rep(UnionList),
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( if UnionList = [Element1 | Rest1] then
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Element = Element1,
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Rest = Rest1
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else
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error("unexpected non-empty list")
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)
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).
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print_myset_rep(set_rep(List), !IO) :-
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print("set_rep(", !IO),
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print(List, !IO),
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print(")", !IO).
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