Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!ut-sally!husc6!uwvax!rutgers!caip!clyde!watmath!watnot!watdaisy!gvcormack
From: gvcormack@watdaisy.UUCP (Gordon V. Cormack)
Newsgroups: net.lang
Subject: x < y < z  using user-defined types and overloading
Message-ID: <7934@watdaisy.UUCP>
Date: Fri, 17-Oct-86 14:04:02 EDT
Article-I.D.: watdaisy.7934
Posted: Fri Oct 17 14:04:02 1986
Date-Received: Sat, 18-Oct-86 23:48:02 EDT
Distribution: net
Organization: U of Waterloo, Ontario
Lines: 27

There has been discussion in the net on languages that allow the
notation                   x < y < z
as a shorthand for         x < y  and  y < z

With user-defined types and overloaded operators (like in Ada)
this is easy to set up (I will spare you the tedious Ada Syntax).

type tempresult = record
                     val: real
                     tst: bool
                  end

operator "<" (a: real, b: real) bool =  ... the normal comparison

operator "<" (a: real, b: real) tempresult =
                (val => b, tst => a < b)

operator "<" (a: tempresult, b: real) bool =
                (a.tst and a.val < b)

operator "<" (a: tempresult, b: real) tempresult =
                (val => b, tst => a.tst and a.val < b)

Aren't data types wonderful?
-- 
Gordon V. Cormack      CS Department, University of Waterloo
   gvcormack@watdaisy.uucp     gvcormack%watdaisy@waterloo.csnet