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bug#6591: 24.0.50; incorrect doc for `catch'

From: Drew Adams
Subject: bug#6591: 24.0.50; incorrect doc for `catch'
Date: Mon, 12 Jul 2010 11:30:19 -0700

> > But you and Eli do not agree about `...' apparently.  For 
> > him `...' does not signify repetition
> That's not true.  I simply wanted to remove the dots.

Careful.  "Signify repetition" of what?  I was speaking of signifying repetition
of _what it follows_.

You made it clear that BODY is not repeated, that `...' does _not_ signify that
what it follows (in this case BODY) is repeatable.

You said, "Saying that there are multiple BODYs breaks the model".  And that
sounds good to me - there is only one body, we have agreed.

Read carefully what I wrote.  This is about whether postfix `...' means that
_what it follows_ is repeatable, not whether BODY or `BODY...' might somehow
signify that _something_ is repeatable - something _other than_ BODY itself.

It's a _syntax_ description.  `...' must apply to something (or to some things)
that is (are) present in the same syntax description.  If it does not apply to
BODY, then what does it apply to?

For most of the world, `X...' suggests that X can be repeated.  You made it
clear that `BODY...' does not mean that BODY itself can be repeated (there can
be only one BODY).

You have chosen to omit the _something_ that is repeatable from the syntax
description and describe it only in the accompanying text, which says that BODY
is one or more forms.  Nothing wrong with that.

But in that case `...' does not signify repetition of anything in the syntax
description.  It is the _accompanying text_ that says that BODY is a repetition
of Lisp forms.  The syntax description can only be said to indicate that if we
explain that `X...' stands for a spliced-in list of Lisp forms.  That (unusual)
definition of `...' is missing from the doc.

That's the choice: how to use `...' - what it should mean.  I'm OK with your
position that it should indicate a &rest parameter, IOW that it should be a
postfix version of `.' (dotted pair operator).  That is not the same as saying
that it signifies repetition of what it follows (in the syntax description).

But (a) that convention needs to be described somewhere and (b) it is not the
typical convention for `...' in syntax descriptions, so we need to take care
here and there to make it clear.

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