Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!wuarchive!uunet!munnari.oz.au!goanna!ok
From: ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe)
Newsgroups: comp.lang.prolog
Subject: Re: why do i need an extra carridge return?
Message-ID: <5481@goanna.cs.rmit.oz.au>
Date: 1 May 91 05:51:35 GMT
References: <9104262300.AA24421@thunder.LakeheadU.Ca> <1991Apr29.102537.12322@canon.co.uk>
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 35

In article <1991Apr29.102537.12322@canon.co.uk>, imlah@canon.co.uk (Bill Imlah) writes:
> Here is some working code.  Prolog gurus: I'm a mere user so if 
> you're going to flame it, flame it in a nice way, as Dame Edna
> would say...

The code keeps on passing around a rather pointless [].
Worse, it is not steadfast.  We want a definition which says
	"get_chars(Chars)
	 reads a line of characters from the current input stream
	 then succeeds if Chars unifies with those characters."

Improved code after the "%"s.

>     read_line(L):-		% get_chars(Chars) :-
>    	get_chars([],L).	%     get0(C),
				%     get_chars_1(C, Cs),
				%     Chars = Cs.  % do this LAST, be steadfast

>    get_chars(IN,OUT):-
> 	get0(C),
> 	get_rest(C,IN,OUT).	% get_chars_1(-1, _) :- !, fail.
> 				%     % do _something_ to handle end of file.
				%     % you may have a better idea.
>    get_rest(10,L,L):-		% get_chars_1(10, []) :- !.
> 	!.			%     % change 10 to 13 on Macintoshes.
>    get_rest(C,IN,[C|OUT]):-	% get_chars_1(C, [C|Cs]) :-
> 	get_chars(IN,OUT).	%     get0(D),
				%     get_chars_1(D, Cs).

Quintus users, of course, already have suitable operations in
library(lineio), which is described in the manual.

-- 
Bad things happen periodically, and they're going to happen to somebody.
Why not you?					-- John Allen Paulos.