X-VM-v5-Data: ([nil nil nil nil nil nil nil t nil]
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Date:         Mon, 11 Jun 90 21:38:38 GMT
Reply-To: LaTeX-L Mailing list <LATEX-L%DHDURZ1@unido.bitnet>
From: CA_ROWLEY@VAX.ACS.OPEN.AC.UK
Subject:      RE: Optional arguments and hooks
To: Rainer Schoepf <BK4@DHDURZ1.uucp>
Status: R
X-Status: 
X-Keywords:                  
X-UID: 131

> Chris would like to remove all optional arguments, among other reasons
> to avoid the error messages caused by a left square bracket at a point
> where an optional argument may appear.  Actually, nearly all these
> problems will disappear if spaces are longer permitted before [.  That
> is easy to implement and fully covered by the explanation in the LaTeX
> book.
I agree that this will help a lot.

> Re hooks: does it matter whether a hook is a macro or a token register?
> That is an implementation decision.
I cannot think of anywhere that it matters (provided you dont need to
many of them, so that you run out of toks registers!).
Yes, I was partly wanting to know about implementation details (how
wicked of me) but I agree that it is there properties that are more
important.

> At the moment I cannot see a need for something like \subtract@fromhook,
> not in the concept of hook I have in mind.  If you find yourself wanting
> this, you've already made a mistake )-;
or I am just thinking of something different to you: without you fully
specifying your hook as an "abstract data-type" how can i tell if it
is me or you who is mistaken!!
So please let us know what you intend: for example, will additions
always be local, or always global, or will both be allowed, or will
some hooks always be changed locally and others always globally.

> A hook should be used, e.g., to execute cleanup code.
This does not help me much, I am afraid.

I am probably wrong, but I had got the impression that these hooks
were to be used like \everymath. etc.
If this is the case, then there may be things that need to be
permannently "in the hook", whereas other things may be needed only
once, therefore they need to clear themselves; this is one form of
subtracting something from a hook but I agree that this does not need
a new operation, since it is self-destroying.

Also some changes can be made to hold only in a group, if local
hook-changing is allowed.

To summarize: without further information, I cannot decide whether
\suntractfrom@hook.


chris