Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!killer!ames!amdcad!sun!quintus!ok
From: ok@quintus.UUCP (Richard A. O'Keefe)
Newsgroups: comp.lang.prolog
Subject: Re: screen control
Keywords: screen control tput character based
Message-ID: <1034@cresswell.quintus.UUCP>
Date: 29 May 88 04:25:44 GMT
References: <701@mtfmi.UUCP>
Organization: Quintus Computer Systems, Mountain View, CA
Lines: 37

In article <701@mtfmi.UUCP>, dbrod@mtfmi.UUCP (D.BRODERICK) writes:
> If your version of Prolog does not have screen control predicates,
> but you are familiar with the Unix(tm) tput(1) command 

It's worth pointing out that
(a) tput is a System V feature, not present in most BSDs (but SunOS has it).
(b) There are some non-trivial differences between V.2 tput and V.3 tput
    (as I found the hard way when some scripts I wrote on a V.3 system
    didn't work on a V.2 system.)
(c) Some of the things tput returns are numbers, for example
	tput lines
    prints the number of lines on the screen.  Suppose that is 24.
    The "get_tput" script provided by D.BRODERICK will write this as '24',
    which is an atom.  You may want to have another script which writes
    things unquoted so that you can access such terminal properties.
(d) Some of the things tput reports are "boolean", for example
	tput hc		# is it a hard-copy terminal?
    always prints nothing.  Instead the answer is to be found in the exit
    code (0 means yes, non-zero means no).  You may want a third script
	if tput -T$1 $2 ; then
	    echo "tput($2, '$1', true)."
	else
	    echo "tput($2, '$1', false)."
	fi
    for use with boolean capabilities.
(e) tput writes things out verbatim, without escape characters.  Some
    Prolog systems may discard CRs or do other odd things with strange
    characters.  (Quintus Prolog is safe, but watch out for terminal
    capabilities containing apostrophes.)  

If the Prolog dialect you are using has an interface to C (as many have)
you would be better off writing an interface to 'curses'; since 'curses'
is available for IBM PCs and VAX/VMS as well as for UNIX this may be more
portable than using tput.  In particular, if you use curses, you don't
have to figure out how to parse the 'cup' capability (rather hairy).
Then too, I for one would rather hide the rather bizarre capability
names (quickly now:  what does eslok do?)  from my Prolog code.