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Estimated hours taken: 0.1 Branches: main NEWS: library/bool.m: Add `pred_to_bool(P) = (if P then yes else no)'.
119 lines
3.1 KiB
Mathematica
119 lines
3.1 KiB
Mathematica
%---------------------------------------------------------------------------%
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% Copyright (C) 1996-1997,2000,2002-2003 The University of Melbourne.
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% This file may only be copied under the terms of the GNU Library General
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% Public License - see the file COPYING.LIB in the Mercury distribution.
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%---------------------------------------------------------------------------%
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% File: bool.m.
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% Main authors: fjh, zs.
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% Stability: medium to high.
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% This module exports the boolean type `bool' and some operations on bools.
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%-----------------------------------------------------------------------------%
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%-----------------------------------------------------------------------------%
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:- module bool.
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:- interface.
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:- import_module enum, list.
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%-----------------------------------------------------------------------------%
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% The boolean type.
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% Unlike most languages, we use `yes' and `no' as boolean constants
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% rather than `true' and `false'. This is to avoid confusion
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% with the predicates `true' and `fail'.
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:- type bool ---> no ; yes.
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:- instance enum(bool).
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:- func bool__or(bool, bool) = bool.
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:- pred bool__or(bool, bool, bool).
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:- mode bool__or(in, in, out) is det.
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:- func bool__or_list(list(bool)) = bool.
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:- pred bool__or_list(list(bool), bool).
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:- mode bool__or_list(in, out) is det.
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:- func bool__and(bool, bool) = bool.
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:- pred bool__and(bool, bool, bool).
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:- mode bool__and(in, in, out) is det.
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:- func bool__and_list(list(bool)) = bool.
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:- pred bool__and_list(list(bool), bool).
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:- mode bool__and_list(in, out) is det.
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:- func bool__not(bool) = bool.
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:- pred bool__not(bool, bool).
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:- mode bool__not(in, out) is det.
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% pred_to_bool(P) = (if P then yes else no).
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:- func pred_to_bool((pred)) = bool.
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:- mode pred_to_bool((pred) is semidet) = out is det.
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%-----------------------------------------------------------------------------%
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:- implementation.
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:- instance enum(bool) where [
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to_int(Bool) = bool_to_int(Bool),
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from_int(bool_to_int(Bool)) = Bool
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].
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:- func bool_to_int(bool) = int.
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:- mode bool_to_int(in) = out is det.
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:- mode bool_to_int(out) = in is semidet.
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bool_to_int(no) = 0.
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bool_to_int(yes) = 1.
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bool__or(X, Y) = Result :- bool__or(X, Y, Result).
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bool__or(yes, _, yes).
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bool__or(no, Bool, Bool).
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bool__or_list(List) = Result :- bool__or_list(List, Result).
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bool__or_list([], no).
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bool__or_list([Bool | Bools], Result) :-
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( Bool = yes ->
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Result = yes
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;
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bool__or_list(Bools, Result)
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).
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bool__and(X, Y) = Result :- bool__and(X, Y, Result).
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bool__and(no, _, no).
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bool__and(yes, Bool, Bool).
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bool__and_list(List) = Result :- bool__and_list(List, Result).
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bool__and_list([], yes).
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bool__and_list([Bool | Bools], Result) :-
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( Bool = no ->
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Result = no
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;
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bool__and_list(Bools, Result)
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).
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bool__not(X) = Result :- bool__not(X, Result).
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bool__not(no, yes).
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bool__not(yes, no).
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:- func bool__return_no = bool.
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:- func bool__return_yes = bool.
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:- pragma export(bool__return_no = out, "ML_bool_return_no").
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:- pragma export(bool__return_yes = out, "ML_bool_return_yes").
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bool__return_no = no.
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bool__return_yes = yes.
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pred_to_bool(P) = (if P then yes else no).
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%-----------------------------------------------------------------------------%
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