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From: ka@hou3c.UUCP (Kenneth Almquist)
Newsgroups: net.lang
Subject: Re: APL myths
Message-ID: <658@hou3c.UUCP>
Date: Wed, 4-Jul-84 14:08:38 EDT
Article-I.D.: hou3c.658
Posted: Wed Jul  4 14:08:38 1984
Date-Received: Thu, 5-Jul-84 00:28:44 EDT
References: <1982@decwrl.UUCP>
Organization: Bell Labs, Holmdel, NJ
Lines: 47

> Another reason why I find APL more readable is its terseness.  One short APL
> expression (average) could be several lines (or pages) of FORGOL:
>
>	DCL I integer;
>	dcl sum integer;
>
>	sum = 0;
>	do i = 1 to length(vector)
>	   sum = sum + vector(i);
>	   end;
>	print sum/length(vector);
>
> as opposed to the APL definition (written here in ascii-ized form):
>
>	(+/ VECTOR) % rho VECTOR

In PL/1 (one of the languages covered under the term "FORGOL") the
example becomes:
	sum(vector) / dim(vector)

Hardly a big difference from the APL version.

> I'm afraid that you've betrayed your lack of knowlege of APL by asking for
> a way to write structured APL (saying that you've used it, is different
> than saying that you understand it).   One of the best elements of APL is
> that it attempts to substitute powerful notation for procedural specification
> (structured programming is a concept of procedural languages which APL tries
> NOT to be).

If APL tries not to be a procedural language, it certainly does not succeed.
In ADA, I can write "array1 := array2" as a single assignment statement
rather than setting up a loop.  In PL/1 I can go farther, writing
"array1 = array2 + array3".  In FORTRAN, a matrix multiplication
is typically a single subroutine call requiring the programmer to
write no loops.

> In other words, SP concepts aren't as necessary in APL because
> the vast majority of loops and things, are eliminated because of APLs
> powerful set of functions and operators.

The vast majority of loops may be eliminated in APL, but what do you
mean by saying that "things" are eliminated?  I agree that APL frees
the programmer from writing a lot of loops, but I don't see how it
eliminates any other gotos.  Since FORTRAN has a "do" loop, you can
have loops in FORTRAN without using gotos.  So why is there any less
need for Rat-APL than for Ratfor?
				Kenneth Almquist