print_message_lines/3

Synopsis

print_message_lines(+Stream, +Prefix, +Lines)

Print the Lines to Stream, preceding each line with Prefix. Note that print_message_lines/3 only succeeds if Lines is a list of pair.

Arguments

Stream stream_object

Any valid output stream.

Prefix term

Any term.

Lines list

is of the form [Line1, Line2, ...], where each Linei is of the form [Control_1-Args_1,Control_2-Args_2, ...].

Description

This command is intended to be used in conjunction with message_hook/3. After a message is intercepted using message_hook/3, this command is used to print the lines. If the hook has not been defined, the arguments are those provided by the system.

print_message_lines/3 is a simple failure driven loop over the Lines data structure, implemented as:

     :-use_module(library(basics),[member/2]).
     
     print_message_lines(Stream,Prefix,Lines):-
         member(Line,Lines),
         format(Stream,'~N~w',[Prefix]),
         (   member(C-A,Line),
             format(Stream,C,A)
         ;   nl(Stream)
         ),
         fail.
     print_message_lines(_,_,_).
     

Exceptions

Any exception that format/3 might raise.

Examples

A typical use of this would be when using the user defined predicate, message_hook/3 to redirect output. For example:

     message_hook(_,_,Lines):-
         my_stream(MyStream),
         print_message_lines(MyStream,'',Lines).
     

See Also:

message_hook/3, print_message/2, generate_message/3, query_hook/6