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Date:	Fri, 13 Feb 2004 11:34:58 PST8
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com
Subject:	SCOUG-Programming: PL/I most important statement (was: call(TZ) ? - PL/I)

Content Type: text/plain

Lynn H. Maxson wrote:
>
> > [the most important PL/I statement - Peter suggested BEGIN]
>
> The BEGIN statement in PL/I has two functions.
> - One, to mark the beginning of an "ON" code subroutine,
> for which purpose they could have easily used the "PROC"
> statement.
> - The second function allows a redeclaration of a variable
> within a code segment to differentiate it from an
> identically named variable in the same procedure but
> outside the code segment. That would allow two or more
> programmers to independently write segments of a program
> without concern for the variable names used.

Okay, good. I thought BEGIN also did memory allocation for whatever was
needed within its block. Yes? No?

> I feel the most important [statement] is probably the
> assignment statement in its support of aggregate operands
> as well as allowing mixed operators (string, arithmetic,
> and boolean) within an expression.

That was my second choice, right after BEGIN. You can't get much work
done without an assignment statement.

I *think* you're including expressions when you say assignment
statement, yes? Expressions can appear in a lot of places, of course,
but we usually think of them as being primarily a part of assignment
statements. First you evaluate the expression, then you "assign" the
result to the target variable.

> I don't want to slight the PL/I builtin functions either.

This choice is perplexing. Syntactically they just look like subroutine
calls, and code-generation-wise they're simply inlined. What's so
special about them?

> Or maybe even the "SIGNAL" statement which supports
> programmer- as well as system-defined interrupts, i.e.
> exception conditions.

Do you think PL/I's exception implementation is stronger than what is in
other popular languages?

- Peter

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