[OS X TeX] environment question

[Alan Munn]

At 12:03 PM -0400 5/19/09, Art Werschulz wrote:
>Hi.
>
>I have created an environment called "offset", which I use for 
>material that needs to be offset from the main text flow.  Here is a 
>small LaTeX file that illustrates its definition and use.
>
><snip>
>\documentclass{article}
>
>\newenvironment{offset}[1]%
>   {\bigskip\hrule\nopagebreak[4]\bigskip\nopagebreak[4]\noindent%
>       \textbf{#1}\nopagebreak\par\medskip\nopagebreak\noindent}%
>   {\nopagebreak[4]\bigskip\hrule\bigskip}
>
>\begin{document}
>My first example is
>\begin{offset}{Addition rule (elementary version)}%
>   Given two disjoint events, $E_1$ and $E_2$, with associated
>   probabilities P($E_1$) and P($E_2$), the probability of $E_1$
>   \emph{or} $E_2$ occurring is equal to
>   to $P(E_1) + P(E_2)$.  That is,
>   \[P(E_1 \cup E_2) = P(E_1) + P(E_2)\]
>   if $E_1$ and $E_2$ are disjoint.
>\end{offset}
>As you can see, this looks pretty good.
>
>My second example is:
>\begin{offset}{Addition rule (general version)}%
>    Given events $E_1$ and $E_2$, with associated
>    probabilities $P(E_1)$ and $P(E_2)$, the probability of $E_1$
>    \emph{or} $E_2$ occurring is
>    \[P(E_1\cup E_2) = P(E_1) + P(E_2) - P(E_1 \cap E_2)\]
>\end{offset}
>That extra space between the math display and the horizontal line is
>ugly.
>
>\end{document}
></snip>
>
>Note the following:
>(1) The comment about the extra (vertical) space.
>(2) I need to put a % after the argument, to avoid an extra horizontal space.
>Any ideas how to fix this?  Is there something pre-existing that I 
>can use instead?

For (2) do the following:

\newenvironment{offset}[1]%
   {\bigskip\hrule\nopagebreak[4]\bigskip\nopagebreak[4]\noindent%
       \textbf{#1}\nopagebreak\par\medskip\nopagebreak\noindent\ignorespaces}%
   {\nopagebreak[4]\bigskip\hrule\bigskip}

For (1) you could put

\belowdisplayshortskip{1ex plus .5ex minus .5ex}

at the beginning of the environment, but this will also affect 
displayed math other places within the environment. (And this still 
might look like too much space)

If this is not a very common occurrence you could not change the 
\belowdisplayshortskip and just put

\vspace{-3.5ex} after and displayed equation that is last in the environment:

\begin{offset}{Addition rule (general version)}
    Given events $E_1$ and $E_2$, with associated
    probabilities $P(E_1)$ and $P(E_2)$, the probability of $E_1$
    \emph{or} $E_2$ occurring is
    \[P(E_1\cup E_2) = P(E_1) + P(E_2) - P(E_1 \cap E_2)\]
    \vspace{-3.5ex}
\end{offset}

Ideally if there was a way to check whether the last element in the 
environment was the end of a display or not you could put the \vspace 
command within a conditional in the environment itself, but I don't 
think there is any way to check that sort of thing.

Alan




-- 
Alan Munn						amunn at msu.edu
Department of Linguistics
and Germanic, Slavic, Asian and African Languages		Tel. 
	517-355-7491
Michigan State University, East Lansing MI 48824 USA	Fax	517-432-2736