X-VM-v5-Data: ([nil nil nil nil nil nil nil t nil]
	[nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil nil])
Date:         Thu, 24 May 90 16:23:54 -0700
Reply-To: LaTeX-L Mailing list <LATEX-L%DHDURZ1@unido.bitnet>
From: Leslie Lamport <lamport@SRC.DEC.COM>
Subject:      Re: Parameters/attributes
To: Rainer Schoepf <BK4@DHDURZ1.uucp>
Status: R
X-Status: 
X-Keywords:                  
X-UID: 111


A few more thoughts on parameters.  First, the implementation isn't as
trivial as I had thought.  The definition of environment foo should
include an explicit \parameters command to insert the parameter
definitions at that point.  For example, if

     \begin{result}[\set{\name}{Zorn's Lemma}]

is to work right, one must have

    \def\result{\let\name=\relax\parameters
       \ifx\name\relax...

So \begin{foo} must push parameters on a stack before calling \foo, and
\parameters must pop them from the stack and execute the commands.
However, what about the naive user who doesn't want to know about
\parameters?  Perhaps there should be two versions of
\newenvironment--one that requires a \parameter and another that
automatically inserts a \parameter.

I agree that it is dangerous to let the user put arbitrary commands
into a parameter declaration.  So, it would be nice to use a syntax
that simply allows setting parameters--something like

    \begin{itemize|topsep=12pt|tick=---}

But, despite Chris Rowley's assertion, I am dubious about it being
possible to implement that in a reasonable fashion in TeX, given that:

* It should be legal to reset any reseasonable parameter in this
way--e.g., line width, font size, and user-defined parameters
that are unknown to the \begin command.

* It should work in all reasonable circumstances, and not break
if it happens to appear inside a tabbing environment inside
a minipage inside a \marginpar.

Yes, lots of people implement things like this in TeX 20 times before
breakfast.  Users of their macros discover 20 cases in which it doesn't
work before lunch.  I just don't know any better syntax then

   \begin{itemize}[\setlength{\topsep}{12pt}\setparam{\tick}{---}]

that I would know how to implement.

Leslie