Philippe de Rochambeau wrote: > Hello, > > eclipse seems to go into endless loop when you type > > X = f(X), Y = f(Y), X = Y. This is something "you should not write" according to Prolog semantics :-) In theory, X=f(X) should simply fail, because a variable cannot unify with a term containing the variable itself. But checking at every unification that the resulting term does not contain cycles is quite expensive, so most Prolog systems do not perform the check (by default). In ECLiPSe, you can switch the occur-check on by setting the flag occur_check: [eclipse 1]: set_flag(occur_check,on). Yes (0.00s cpu) [eclipse 2]: X = f(X), Y = f(Y), X = Y. No (0.00s cpu) So, you should write X=f(X) only if you have the occur-check activated; otherwise you know that you may get inconsistent results. Cheers, Marco -- Marco Gavanelli, Ph.D. Computer Science Division Dipartimento di Ingegneria University of Ferrara Via Saragat 1 - 44100 Ferrara (Italy) Tel +39-0532-97-4833 Fax +39-0532-97-4870 http://www.ing.unife.it/docenti/MarcoGavanelli/Received on Wed Jan 10 2007 - 09:31:27 CET
This archive was generated by hypermail 2.3.0 : Tue Apr 16 2024 - 09:13:19 CEST