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From: Richard Stallman <rms@gnu.org>
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Subject: Re: while-no-input
Date: Wed, 02 Oct 2002 15:24:28 -0400
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It is a general principle that to avoid using abnormal
condition handling for programmed control flow.
I think it is very unclean to treat ordinary input
like a quit and then distinguish them later.
So I don't think we should add this mechanism.

It is easy enough to do the job using input-pending-p.
You can use

  (catch 'input
    (...
      (if (input-pending-p) (throw 'input nil))
      ...))

if you want to avoid testing input-pending-p at various
levels in the code.