Hi!

We've found the following error.

Version of SWI-Prolog and operating system:

OS: Linux 4.15.0-74-generic #84-Ubuntu SMP Thu Dec 19 08:06:28 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

SWI-Prolog (threaded, 64 bits, version 7.6.4)

Program that produces the error:

use_module(library(clpq)).
G=(M=<X, X=<N, N1>=0, K>=1, N1 = K-1, K = N-M+1),
{G},
copy_term(G,T),
T=(F,R),
{F}.

The answer is:

false

but it should be something along the lines:

G = (M=<X,X=<N,N1>=0,K>=1,N1=K-1,K=N-M+1),
T = (_A=<_B,_B=<_C,_D>=0,_E>=1,_D=_E-1,_E=_C-_A+1),
F = (_A=<_B),
R = (_B=<_C,_D>=0,_E>=1,_D=_E-1,_E=_C-_A+1),
{N1= -1+K},
{N= -1+M+K},
{M-X=<0},
{_A-_B=<0},
{M-X+K>=1}

According to Paulo Moura this is the answer given by Sictus Prolog.

Besides, the same goal where the order of the integer constraints in G is slightly changed:

G=(M=<X, X=<N, N1>=0, K>=1, K = N-M+1, N1 = K-1),
{G},
copy_term(G,T),
T=(F,R),
{F}.

produces a correct answer.

This error was found by Gianfranco Rossi and me.

All the best,
Maxi