ftp.cs.arizona.edu/ftp.cs.arizona.edu.tar/ftp.cs.arizona.edu/icon/newsgrp/group96a.txt/000062_icon-group-sender _Mon Mar 4 20:58:38 1996.msg

Internet Message Format | 1996-09-05 | 2KB

Received: by cheltenham.cs.arizona.edu; Mon, 4 Mar 1996 16:21:13 MST
From: "Hamish Lawson" <[e-mail]>
Organization:  University of Teesside (SCM)
To: [e-mail]
Date:          Mon, 4 Mar 1996 20:58:38 GMT0BST
Subject:       Production of an operator's left-hand operand
Reply-To: [e-mail]
Priority: normal
X-Mailer: Pegasus Mail for Windows (v2.0-WB2)
Message-Id: <B461B2458B@scm_arkengarthdale.tees.ac.uk>
Errors-To: [e-mail]
Status: O

I understand the logic behind having operators produce their
right-hand operand, in order that we can do stuff like

   if x < y < z then

However I frequently want to have the right-hand operand produced,
e.g to print x only if it is greater than 5 I cannot say

   write(x > 5)

but must instead say

   write(5 < x)

Aside from the slight artificiality in such a construct this
rearrangement may not work (and correct me if I'm wrong) if I want to
do something like printing the value of e1 only if e2 succeeds; that
is, I cannot necessarily rewrite this as

   write(e2 & e1)

Want would be nice would be parallel operators that produce their
left-hand operand; a possible notation would be to prefix the
standard operator with a ^ (there may be better schemes, perhaps a
suffix ~):

   write(e1 ^& e2)  # produces e1 only if e2 succeeds

Aside from the usual problems of getting a new feature adopted in a
language, are their any other problems with such an idea?

| Hamish Lawson, School of Computing and Mathematics,
| University of Teesside, Middlesbrough, Cleveland, UK, TS1 3BA
| Tel: [phone] x3611  Fax: [phone]
| E-mail: [e-mail]