Re: variable analysis

On 08/15/2013 01:18 PM, Carlo Capelli wrote:
> Also my code generates similar warnings
>
> curious_fraction(Nr, Dr) :-
>     Vs = [N1,N2, D1,D2], Vs ins 1..9,
>     N #= N1 * 10 + N2, D #= D1 * 10 + D2, D #> N,
>     select(C, [N1,N2], [Nr]), select(C, [D1,D2], [Dr]),
>     N * Dr #= Nr * D, label(Vs).
>
> generates
>
> Warning: /home/carlo/prolog/coins.pl:129:
>
> Test is always true: var(N)
> Test is always true: var(D)

Clpfd generates redudant code, expecting the compiler to optimize it. I
vaguely knew this. Not really sure how to handle this. You can use

     :- style_check(-no_effect)

to get rid of these. Actually, it traps more in this code, but it is
currently configured to ignore warnings about goals that have no named
variables, assuming these are generated. I guess we either need an
library that can be called to optimize the generated code or we need
some way for term/goal expansion to tell the compiler not to worry about
this code.  Ideas?

	Cheers --- Jan

2 ?- listing(curious_fraction).
curious_fraction(K, M) :-
	A=[B, C, F, G],
	A ins 1..9,
	(   integer(D)
	->  (   var(B*10+C)
	    ->  B*10+C is D
	    ;   integer(B),
		integer(C)
	    ->  D=:=B*10+C
	    ;   E is D,
		clpfd:clpfd_equal(E, B*10+C)
	    )
	;   integer(B),
	    integer(C)
	->  (   var(D)
	    ->  D is B*10+C
	    ;   E is B*10+C,
		clpfd:clpfd_equal(D, E)
	    )
	;   clpfd:clpfd_equal(D, B*10+C)
	),
	(   integer(H)
	->  (   var(F*10+G)
	    ->  F*10+G is H
	    ;   integer(F),
		integer(G)
	    ->  H=:=F*10+G
	    ;   I is H,
		clpfd:clpfd_equal(I, F*10+G)
	    )
	;   integer(F),
	    integer(G)
	->  (   var(H)
	    ->  H is F*10+G
	    ;   I is F*10+G,
		clpfd:clpfd_equal(H, I)
	    )
	;   clpfd:clpfd_equal(H, F*10+G)
	),
	(   integer(H)
	->  (   integer(D)
	    ->  H>=D+1
	    ;   J is H,
		clpfd:clpfd_geq(J, D+1)
	    )
	;   integer(D)
	->  J is D+1,
	    clpfd:clpfd_geq(H, J)
	;   clpfd:clpfd_geq(H, D+1)
	),
	select(L, [B, C], [K]),
	select(L, [F, G], [M]),
	(   integer(D),
	    integer(M)
	->  (   var(K*H)
	    ->  K*H is D*M
	    ;   integer(K),
		integer(H)
	    ->  D*M=:=K*H
	    ;   N is D*M,
		clpfd:clpfd_equal(N, K*H)
	    )
	;   integer(K),
	    integer(H)
	->  (   var(D*M)
	    ->  D*M is K*H
	    ;   N is K*H,
		clpfd:clpfd_equal(D*M, N)
	    )
	;   clpfd:clpfd_equal(D*M, K*H)
	),
	label(A).


> OT: Jan, the jump to source origin of message now make difficult to select
> the text, I will try to fix it...

Making progress ... I have a working MacOS swipl-win.app (well,
proof of concept).

	Cheers --- Jan

>
> bye Carlo
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