Path: utzoo!attcan!uunet!mcvax!hp4nl!eutrc3!euteal!mart
From: mart@euteal.UUCP (Mart van Stiphout)
Newsgroups: comp.lang.misc
Subject: Re: Turing programming language.
Summary: Reaction on Mark Mendells explanation of the Turing syntax.
Keywords: programming language
Message-ID: <12@euteal.UUCP>
Date: 23 Jan 89 22:22:07 GMT
References: <11@euteal.UUCP> <89Jan20.111000est.4328@turing.toronto.edu>
Organization: Eindhoven University of Technology, The Netherlands
Lines: 58



 > I think that loop statement in Turing is simple and easy to use.  It is more
 > powerful than the equivalent Pascal loops.  For example:
 
 Let me explain my objections to the Turing loop syntax.
 My main objection is the location of the exit criterion. It is
 inside the loop and generally will be surrounded by (lots ?) of
 code. As  we all know, the correctness of loops
 can be shown by pre- and postconditions and the
 invariant relation. 
 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. I think it's ok to use different
 notations for different loops
 
 I'm not the greatest C fan, but I think C loops are just what
 you need for correct loops. Let me compare the C and Turing loops:
 
 C						Turing

						initialisation
 for ( initialisation; condition;  increment )	loop
 {			  			  exit when not condition
   ... code ...					  ... code ...
 }						end loop


 initialisation					initialisation
 do {						loop
   ... code ...		  			  ... code ...
 while condition		  			  exit when condition
						end loop

 And what do you think of the following C version of your 1.5 loop?
 while ( i = read() ) {
   ...code...
 }

 > You have a better point with collections.  The Turing syntax:
 
 I really like the idea of indexing linked list as if they were arrays.
 At the moment I am really fed up with the minimal support of
 languages like Pascal and C for linked lists. I always have
 to create records (structs) and `next' pointers. Accessing or
 adding list elements always requires extra source code for
 rather trivial operations.
 Why can't there be a programming language with type list that
 automatically allocates memory if needed and allows treatment of
 list in a similar way as arrays. Arrays are so much easier to
 handle, give fewer errors and the code looks much better.
 I'm really interested in other peoples opinions on these ideas.
 
 ---------------
 Mart van Stiphout
 Eindhoven University of Technology
 email: mart@euteal.eutrc3.hp4nl.mcvac.uucp