% module:   print_chars
% date:     November 21, 2005
% author:   Douglas M. Auclair

% Copyright (c) 2005, Cotillion Group, Inc. All rights reserved.

% synopsis: Facilitates porting applications between Quintus and SWI by 
%           providing skeletal implementations of these Quintus modules
%           to SWI.

:- module(print_chars, []).

% modified: December 8, 2005, DMA
% changed:  Passed in the max number of characters we wish to see

% modified: December 6, 2005, DMA
% changed:  Added assertation to print the list as a string, given that 
%	    every member is a character (an integer) and that every 
%	    character is printable.

:- asserta((user:portray(Chars) :-
		improper_string(60, Chars, Last, [Char|S], []),
		(\+ (\+ Last = '_|_') ->
		    format('["~s"|~p]', [[Char|S], Last])
                 ;
		    (\+ (\+ Last = []) ->
	                format('"~s"', [[Char|S]])
		     ;
		        format('["~s"|~p]', [[Char|S], Last]))))).
:- asserta((user:portray(L1-L2) :-
		print_chars:difference_string(60, L1-L2, String, []),
                format('["~s"|_L]-_L', [String]))).

difference_string(X, [Char|L1] - L2) -->
  { X > 0, Y is X - 1, integer(Char), Char > 9, Char < 128 },
  [Char],
  difference_string(Y, L1 - L2).
difference_string(0, _) --> !, "...".
difference_string(_, L1 - L1) --> [].

improper_string(X, [Char|T], Last) -->
  { X > 0, Y is X - 1, integer(Char), Char > 9, Char < 128 },
  !,
  [Char],
  improper_string(Y, T, Last).
improper_string(0, _Last, "...") --> !.
improper_string(_, Last, Last) --> [].