Path: utzoo!attcan!uunet!mcvax!ukc!etive!lfcs!db
From: db@lfcs.ed.ac.uk (Dave Berry)
Newsgroups: comp.lang.misc
Subject: Re: Turing programming language.
Keywords: programming language
Message-ID: <1284@etive.ed.ac.uk>
Date: 24 Jan 89 14:57:05 GMT
References: <11@euteal.UUCP> <89Jan20.111000est.4328@turing.toronto.edu> <12@euteal.UUCP>
Sender: news@etive.ed.ac.uk
Reply-To: db@lfcs.ed.ac.uk (Dave Berry)
Organization: Laboratory for the Foundations of Computer Science, Edinburgh U
Lines: 42

In article <12@euteal.UUCP> mart@euteal.UUCP (Mart van Stiphout) writes:
> In my view, the stop criterion should not be located somewhere in the
> middle of the loop. Furthermore, in my opinion your Pascal
> examples of loops proof their superiority to the Turing loops:
> the loop type is clear in a glance.

Two points:
  1) exits from loops make some programs easier to write and understand.
  2) a slightly different indentation scheme can make them just as easy to
     read (IMO) as Pascal type loops.
     
The first point is discussed with supporting psychological evidence in
the following article:

@Article(soloway2,
      Author="E. Soloway and J. Bonar and K. Ehrlich",
      Title="Cognitive Strategies and Looping Constructs: An Empirical Study",
      Journal="CACM",
      Volume="26",
      Pages="853-860",
      Year="1983")

The second point is clearly subjective, but I think that if you don't
indent exit statements, loops are easy to read:

exit indented:				exit not indented:

initialisation				initialisation
loop					loop
  some code				  some code
  exit when condition			exit when condition
  some more code			  some more code
end loop				end loop

> I'm not the greatest C fan, but I think C loops are just what
> you need for correct loops.

Presumably you want to exclude the break statement!

Dave Berry,	Laboratory for Foundations of Computer Science, Edinburgh.
		db%lfcs.ed.ac.uk@nss.cs.ucl.ac.uk
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