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Re: select syntax violates the POLA

From: Robert Elz
Subject: Re: select syntax violates the POLA
Date: Fri, 09 Apr 2021 00:45:28 +0700

    Date:        Wed, 07 Apr 2021 22:24:27 -0400
    From:        worley@alum.mit.edu (Dale R. Worley)
    Message-ID:  <87a6q9ikdg.fsf@hobgoblin.ariadne.com>

  | "The documentation is the contract between the user and
  | the implementer."  If something undocumented happens to work, there is
  | no requirement on the implementer to maintain its functionality.

That might, or might not, be true - in both directions (implementors
are often constrained to keep old things, that were never documented,
working, because they became known, and are used - similarly some
things were once documented, but are no longer, as a better solution
was implemented - but the old undocumented code has to stay, essentially
forever, for the benefit of those who used it when it was documented).

But whatever all that ends up meaning, if anything significant here,
it certainly does not mean that the implementation is required to
reject extensions that are not documented.   Or that it is any kind
of bug for it not to do so.

As long as you stick to using the implementation as documented (you
keep up your end of the "contract"), you will never observe this happening.
But when someone else does not, and asks about something that looks like
it is using undocumented behaviour, it might be OK to suggest to them
that what they're doing is unsafe - but not to suggest that the implementation
should reject what they are doing.

That is ' "{" should not be recognized as a reserved word in this situation. '
is simply wrong.  The situation mentioned was "else {", which actually is
documented as working, but never mind.


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