104 lines
2.8 KiB
Plaintext
104 lines
2.8 KiB
Plaintext
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/*
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This file contains an adaptation to Logtalk of code for logical assignment
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of Prolog terms developed by Nobukuni Kino. For more information, please
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consult the URL http://www.kprolog.com/en/logical_assignment/
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As a derivative work, this file is licensed under the Open Software License
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version 2.1 (http://opensource.org/licenses/osl-2.1.php).
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*/
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:-op(100, xfx, '<=').
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:-op(100, xfx, '=>').
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:- category(assignvars).
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:- info([
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version is 1.0,
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author is 'Nobukuni Kino and Paulo Moura',
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date is 2005/1/7,
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comment is 'Assignable variables (supporting logical, backtracable assignement of non-variable terms).']).
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:- public(assignable/1).
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:- mode(assignable(-assignvar), one).
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:- info(assignable/1, [
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comment is 'Makes Variable an assignable variable. Initial state will be empty.',
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argnames is ['Variable'],
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exceptions is [
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'Variable is not a variable' - type_error(variable, 'Variable')]]).
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:- public(assignable/2).
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:- mode(assignable(-assignvar, @nonvar), one).
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:- info(assignable/2, [
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comment is 'Makes Variable an assignable variable and sets its initial state to Value.',
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argnames is ['Variable', 'Value'],
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exceptions is [
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'Variable is not a variable' - type_error(variable, 'Variable'),
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'Value is not instantiated' - instantiation_error]]).
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:- public((<=)/2).
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:- mode(<=(?assignvar, @nonvar), one).
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:- info((<=)/2, [
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comment is 'Sets the state of the assignable variable Variable to Value (initializing the variable if needed).',
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argnames is ['Variable', 'Value'],
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exceptions is [
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'Value is not instantiated' - instantiation_error]]).
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:- public((=>)/2).
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:- mode(=>(+assignvar, ?nonvar), zero_or_one).
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:- info((=>)/2, [
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comment is 'Unifies Value with the current state of the assignable variable Variable.',
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argnames is ['Variable', 'Value'],
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exceptions is [
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'Variable is not instantiated' - instantiation_error]]).
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:-op(100, xfx, <=).
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:-op(100, xfx, =>).
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assignable(Assig) :-
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nonvar(Assig),
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self(Self),
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sender(Sender),
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throw(error(type_error(variable, Assig), Self::assignable(Assig), Sender)).
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assignable([_| _]).
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assignable(Assig, Init) :-
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nonvar(Assig),
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self(Self),
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sender(Sender),
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throw(error(type_error(variable, Assig), Self::assignable(Assig, Init), Sender)).
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assignable(Assig, Init) :-
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var(Init),
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self(Self),
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sender(Sender),
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throw(error(instantiation_error, Self::assignable(Assig, Init), Sender)).
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assignable([_, Init| _], Init).
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Assig <= Value :-
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var(Value),
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self(Self),
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sender(Sender),
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throw(error(instantiation_error, Self::Assig <= Value, Sender)).
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[_| Tail] <= Value :-
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nonvar(Tail) ->
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Tail <= Value
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;
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Tail = [Value| _].
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Assig => Value :-
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var(Assig),
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self(Self),
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sender(Sender),
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throw(error(instantiation_error, Self::Assig => Value, Sender)).
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[Current| Tail] => Value :-
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nonvar(Tail) ->
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Tail => Value
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;
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Current = Value.
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:- end_category.
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