Path: utzoo!utgpu!attcan!uunet!seismo!sundc!pitstop!sun!chiba!khb
From: khb%chiba@Sun.COM (Keith Bierman - Sun Tactical Engineering)
Newsgroups: comp.lang.fortran
Subject: Re: Why array notation
Message-ID: <76259@sun.uucp>
Date: 4 Nov 88 20:22:06 GMT
References: <689@convex.UUCP>
Sender: news@sun.uucp
Reply-To: khb@sun.UUCP (Keith Bierman - Sun Tactical Engineering)
Organization: Sun Microsystems, Mountain View
Lines: 47

In article <689@convex.UUCP> mercer@mozart.UUCP (Randall Mercer) writes:
>Does anyone know why FORTRAN-8x uses array notation rather than some 
>form of parallel do loop?  What is the advantage of writing
>
>	A(1:N)=B(2:N+1)+C(1:N)
>
>rather than something like:
>
>	PDO 10 I=1,N			! PDO for "PARALLEL DO"
>10      A(I)=B(I+1)+C(I)
>
>The latter requires minimal syntactic changes and, for long loops, is
>more concise and readable.  Is the problem with the details of defining
>"PDO", or is it some more strategic reason?

As I recall, there were several reasons:

1)	Array notation was originally attractive to hardware types,
	and was intended to be relatively easy for existing and proposed
	array processors.

2)	Arrays are a mathematical "first class object" and providing
	them in the language will help fill a semantic gap between
	what scientists write, and what computers want.

3)	To a certain extent, it is adopting current practice, as
	extended fortrans (like the Q8 facility in CDC fortran) have
	similar notation.

4)	related to 2: in the most common case, where we want to
	operate on the arrays in the "natural" fashion, it is simpler, viz

		A = B+C  

	I think your case translates as

	        A = B(2:N+1)+C

Parallel structures were considered to be too researchy to be in f88,
array operations were not (since they do exist in some fortrans, all
APL's, and many other research languages).

Members of the committee (rather than Observers like myself) may have
more detailed recollections.

Keith H. Bierman
It's Not My Fault ---- I Voted for Bill & Opus