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Date:	Sun, 17 Apr 2005 20:30:02 PDT7
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com
Subject:	SCOUG-Programming: Stirring the Pot - data type defaults and declarations

Content Type: text/plain

Sheridan George wrote:
>
> My suggestion is to get off the sticky pad of the merits of PL/I, APL2, and LISP and agree our SL/1
> language should have the data types of PL/I, the operations of APL2 (enhanced with the list
> aggregate from LISP), but with the ease of use of Python. I don't want to see "declare this,
> declare that, allocate this, deallocate that, begin/end, and semi-colons". Let the interpreter and
> compiler do all of that nasty work. If Python can do it so can SL/1.

You are correct that declarations aren't necessary. Rexx is used on
mainframes and as far as I know never declares any particular data
types.

Four comments:

-- 1. Of great importance to this discussion: at times it is a matter
of defaults. In PL/I if you don't declare INDEX it becomes the default
(for I-N names) type Fixed Binary (just like Fortran). In Rexx,
however, the default (for everything) is an unlimited character
string. If you want anything-goes defaults then that's fine; if you
want restrictive defaults then that's okay too. This is as simple as a
compiler/interpreter option -- declare your data defaults to be PL/I, or
Fortran/Rexx, or whatever you like. "Choosing the right tool for the
job" might in part just be what kind of data type defaults you want to
work with.

-- 2. Sometimes you want to declare a specific data type for inline
error checking. Rexx has no way of knowing that INDEX is always a
number, and thus allows INDEX='XYZ'. Some programmers like to catch
these bugs early rather than at run time.

-- 3. Sometimes a declaration can speed up the execution. In my number
crunching I'd rather use an 8-bit value in a loop than a 64-bit value
because I'm convinced it will execute faster. Different hardware can
affect this, but I'm old-fashioned and prefer legacy support.

-- 4. Sometimes you want to declare a specific data type for
compatibility with incoming data. If your tape drive or satellite feed
is supplying you with BCD you may want to declare the variable receiving
the data as BCD rather than receiving it as binary and then converting
it.

In Summary: Different languages offer different default data types and
ways to force specific data types. It would be very simple to allow a
choice of default data type(s) in a language; alternately you can choose
a language for a project based on the specific default data types and
allowed data types that it offers.

- Peter

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