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From: "Jeffrey R.Carter" <spam.jrcarter.not@spam.acm.org.not>
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Subject: Re: Map iteration and modification
Date: Sun, 7 Jan 2024 16:06:10 +0100
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On 2024-01-06 08:25, Randy Brukardt wrote:
> 
> @ is regular in the sense that it is allowed anywhere in an expression. If
> you tried to expand the use to other contexts, you would have to
> differentiate them, which would almost certainly require some sort of
> declaration. But doing that risks making the mechanism as wordy as what it
> replaces (which obviously defeats the purpose).
> 
> We looked at a number of ideas like that, but they didn't seem to help
> comprehension. In something like:
>     LHS:(X(Y)) := LHS + 1;
> (where LHS is an arbitrary identifier), if the target name is fairly long,
> it could be hard to find where the name for the target is given, and in any
> case, it adds to the name space that the programmer has to remember when
> reading the source expression. That didn't seem to add to readability as
> much as the simple @ does.
> 
> In any case, these things are trade-offs, and certainly nothing is absolute.
> But @ is certainly much more general than ":=+" would be, given that it
> works with function calls and array indexing and attributes and user-defined
> operations rather than just a single operator.

For the 9X and 0X revisions I suggested adding "when <condition>" to return and 
raise statements, similar to its use on exit statements. This was rejected 
because the language already has a way to accomplish this: if statements.

Given that one can do

declare
    V : T renames Very_Long_Identifier;
begin
    V := V - 23;
end;

it seems that @ should also have been rejected. Probably more so, since @ is 
completely new syntax rather than reusing existing syntax on some additional 
statements. What is the justification of accepting @ while still rejecting the 
other?

-- 
Jeff Carter
"If I could find a sheriff who so offends the citizens of Rock
Ridge that his very appearance would drive them out of town ...
but where would I find such a man? Why am I asking you?"
Blazing Saddles
37