Two standard functions are available to print standard Prolog errors to the standard error stream.
.BF .F int PL_warning 1 format, a1, ... Print an error message starting with `[WARNING: ', followed by the output from format, followed by a `]' and a newline. Then start the tracer. format and the arguments are the same as for printf(2). Always returns FALSE. .F void PL_fatal_error 1 format, a1, ... Print a message like PL_warning(), but starting with `FATAL ERROR: ' and then exits Prolog. .EF