Path: utzoo!mnetor!uunet!husc6!sri-unix!quintus!ok
From: ok@quintus.UUCP (Richard A. O'Keefe)
Newsgroups: comp.lang.prolog
Subject: Re: BSI standards
Message-ID: <751@cresswell.quintus.UUCP>
Date: 10 Mar 88 09:01:20 GMT
References: <8803082357.AA01587@decwrl.dec.com> <5334@utah-cs.UUCP>
Organization: Quintus Computer Systems, Mountain View, CA
Lines: 26

In article <5334@utah-cs.UUCP>, shebs%defun.utah.edu.uucp@utah-cs.UUCP (Stanley T. Shebs) writes:
> String and list types have good and bad points, but the lack of character
> types in older Prologs is a great embarassment.  Numbers like 26 and 65 
> are sadly common, as is doing arithmetic on these to implement character
> operations.  I think it's safe to say that any language requiring the use
> of numbers to represent some other type of object is not "high level", at
> least with respect to that type.

A distinction:
	the lack of a _notation_ for characters other than the numbers.
	PopLog has `x`, DEC-10 Prolog, (some versions of) C Prolog, and
	Quintus Prolog have 0'x (yes, it's a hack, but there weren't
	any characters left over), ALS Prolog has ~x.

	the lack of a separate datatype for characters.

For once I'm not going to express an opinion!  Comparing Pascal code I've
seen with C suggests that using ORD and CHR a lot isn't a good idea either.
I've used Interlisp enough to know that I *definitely* don't want to use
atoms to represent characters, but I haven't used Common Lisp enough to
know whether that's better.

What problems are people having that could be reduced by having a separate
character type (as opposed to having characters coded as integers but with
a tolerable notation such as `x`)?  Anyone using a Prolog that has such a
data type?