If you want to print a clause, portray_clause/[1,2] is almost
certainly the command you want. None of the other term output commands
puts a full-stop after the written term. If you are writing a file of
facts to be loaded by compile/1, use portray_clause/[1,2], which
attempts to ensure that the clauses it writes out can be read in again
as clauses.
The output format used by portray_clause/[1,2] and listing/[0,1] has been
carefully designed to be clear. We recommend that you use a
similar style. In particular, never put a semicolon (disjunction symbol)
at the end of a line in Prolog.
See mpg-ref-portray_clause.