Uncaught Mercury exception:
Software Error: detected infinite recursion in pred loopcheck.loop/1
Stack dump follows:
   0       pred exception.throw_impl/1-0 (erroneous) (exception.m:NNNN)
   1       pred exception.throw/1-0 (erroneous) (exception.m:NNNN)
   2       pred require.error/1-0 (erroneous) (require.m:NNNN)
   3    2* pred loopcheck.loop/1-0 (erroneous) (loopcheck.m:17)
   5       pred loopcheck.main/2-0 (det) (loopcheck.m:13)