11.3.157 portray_clause/[1,2]

Synopsis

portray_clause(+Clause)

portray_clause(+Stream, +Clause)

Writes Clause to the current output stream. Used by listing/[0,1].

Arguments

Stream

stream_object, must be ground

A valid open Prolog stream, defaults to the current output stream.

Clause

term

Description

The operation used by listing/[0,1]. Clause is written to Stream, in exactly the format in which listing/[0,1] would have written it, including a terminating full stop.

If you want to print a clause, then this is almost certainly the command you want. By design, 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 the Load Predicates, then 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.

Exceptions

Stream errors (see ref-iou-sfh-est).

Examples

| ?- portray_clause((X:- a -> b ; c)).
_ :-
        (   a ->
            b
        ;   c
        ).

| ?- portray_clause((X:- a -> (b -> c ; d ; e); f)).
_ :-
        (   a ->
            (   b ->
                c
            ;   d
            ;   e
            )
        ;   f
        ).

| ?- portray_clause((a:-b)).
a :-
        b.

| ?- portray_clause((a:-b,c)).
a :-
        b,
        c.

| ?- portray_clause((a:-(b,!,c))).
a :-
        b, !,
        c.

See Also

listing/[0,1], ref-iou-tou.