$ cat bug.P bug(Term, N) :- N is Term. [roberto@zoltan tmp]$ $ xsb [xsb_configuration loaded] [sysinitrc loaded]

XSB Version 3.1 (Incognito) of August 10, 2007 [x86_64-unknown-linux-gnu; mode: optimal; engine: slg-wam; gc: indirection; scheduling: local]

| ?- ['bug.P']. [Compiling ./bug] [bug compiled, cpu time used: 0.0080 seconds] [bug loaded]

yes | ?- bug(1+1+1, Y).

Y = 1 + 1 + 1

yes | ?- End XSB (cputime 0.02 secs, elapsetime 365.32 secs)