73 lines
1.1 KiB
Plaintext
73 lines
1.1 KiB
Plaintext
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:- object(_ - _,
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implements(symdiffp)).
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:- info([
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authors is 'Paulo Moura',
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version is 1.0,
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date is 1999/12/29,
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parnames is ['Expression1', 'Expression2'],
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comment is 'Symbolic differentiation and simplification of -/2 expressions.',
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source is 'Example based on the Clocksin and Mellish Prolog book.']).
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diff(Diff) :-
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this(X - Y),
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once(diff(X, Y, Diff)).
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diff(I, J, 0) :-
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integer(I),
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integer(J).
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diff(X, J, DX) :-
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integer(J),
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X::diff(DX).
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diff(I, Y, DY) :-
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integer(I),
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Y::diff(DY).
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diff(X, Y, DX - DY) :-
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X::diff(DX),
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Y::diff(DY).
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simplify(S) :-
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this(X - Y),
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once(simplify(X, Y, S)).
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simplify(X, X, 0).
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simplify(I, J, S) :-
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integer(I),
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integer(J),
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S is I - J.
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simplify(X, 0, S) :-
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X::simplify(S).
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simplify(0, Y, S) :-
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Y::simplify(S).
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simplify(X, J, S - J) :-
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integer(J),
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X::simplify(S).
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simplify(I, Y, I - S) :-
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integer(I),
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Y::simplify(S).
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simplify(X, Y, S) :-
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X::simplify(SX),
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Y::simplify(SY),
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(X - Y \= SX - SY ->
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(SX - SY)::simplify(S)
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;
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S = SX - SY).
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:- end_object.
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