beamer / doc / beamerug-localstructure.tex

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% Copyright 2007 by Till Tantau
%
% This file may be distributed and/or modified
%
% 1. under the LaTeX Project Public License and/or
% 2. under the GNU Free Documentation License.
%
% See the file doc/licenses/LICENSE for more details.

% $Header$

\section{Structuring a Presentation: The Local Structure}

\LaTeX\ provides different commands for structuring text ``locally,''
for example, via the |itemize| environment. These environments
are also available in the \beamer\ class, although their appearance has
been slightly changed. Furthermore, the \beamer\ class also defines
some new commands and environments, see below, that may help you to
structure your text.


\subsection{Itemizations, Enumerations, and Descriptions}

\label{section-enumerate}

There are three predefined environments for creating lists, namely
|enumerate|, |itemize|, and |description|. The first
two can be nested to depth three, but nesting them to this depth
creates totally unreadable slides.

The |\item| command is overlay-specification-aware. If an overlay
specification is provided, the item will only be shown on the
specified slides, see the following example. If the |\item|
command is to take an optional argument and an overlay specification,
the overlay specification can either come first as in |\item<1>[Cat]|
or come last as in |\item[Cat]<1>|.

\begin{verbatim}
\begin{frame}
  There are three important points:
  \begin{enumerate}
  \item<1-> A first one,
  \item<2-> a second one with a bunch of subpoints,
    \begin{itemize}
    \item first subpoint. (Only shown from second slide on!).
    \item<3-> second subpoint added on third slide.
    \item<4-> third subpoint added on fourth slide.
    \end{itemize}
  \item<5-> and a third one.
  \end{enumerate}
\end{frame}
\end{verbatim}


\begin{environment}{{itemize}\opt{|[<|\meta{default overlay specification}|>]|}}
  Used to display a list of items that do not have a special
  ordering. Inside the environment, use an |\item| command for
  each topic.
  
  If the optional parameter \meta{default overlay specification} is
  given, in every occurrence of an |\item| command that does not have
  an overlay specification attached to it, the \meta{default overlay
    specification} is used. By setting this specification to be an
  incremental overlay specification, see
  Section~\ref{section-incremental}, you can implement, for example, a
  step-wise uncovering of the items. The \meta{default overlay
    specification} is inherited by subenvironments. Naturally, in a
  subenvironment you can reset it locally by setting it to |<1->|.
  \example
\begin{verbatim}
\begin{itemize}
\item This is important.
\item This is also important.
\end{itemize}
\end{verbatim}
  
  \example
\begin{verbatim}
\begin{itemize}[<+->]
\item This is shown from the first slide on.
\item This is shown from the second slide on.
\item This is shown from the third slide on.
\item<1-> This is shown from the first slide on.
\item This is shown from the fourth slide on.    
\end{itemize}
\end{verbatim}
  
  \example
\begin{verbatim}
\begin{itemize}[<+-| alert@+>]
\item This is shown from the first slide on and alerted on the first slide.
\item This is shown from the second slide on and alerted on the second slide.
\item This is shown from the third slide on and alerted on the third slide.
\end{itemize}
\end{verbatim}
  
  \example
\begin{verbatim}
\newenvironment{mystepwiseitemize}{\begin{itemize}[<+-| alert@+>]}{\end{itemize}}
\end{verbatim}

  \lyxnote
  Unfortunately, currently you cannot specify optional arguments with
  the |itemize| environment. You can, however, use the command
  |\beamerdefaultoverlayspecification| before the environment to get
  the desired effect.

  The appearance of an |itemize| list is governed by several
  templates. The first template concerns the way the little marker
  introducing each item is typeset:  
  \begin{element}{itemize items}\semiyes\no\no
    This template is a parent template, whose children are
    |itemize item|, |itemize subitem|, and |itemize subsubitem|. This
    means that if you use the |\setbeamertemplate| command on this
    template, the command is instead called for all of these children
    (with the same arguments). 

    \begin{templateoptions}
      \itemoption{default}{}
      The default item marker is a small triangle colored with the 
      foreground of the \beamer-color |itemize item| (or, for
      subitems, |itemize subitem| etc.). Note that these colors will
      automatically change under certain circumstances such as inside
      an example block or inside an |alertenv| environment. 
      \itemoption{triangle}{}
      Alias for the default.
      \itemoption{circle}{}
      Uses little circles (or dots) as item markers. 
      \itemoption{square}{}
      Uses little squares as item markers.
      \itemoption{ball}{}
      Uses little balls as item markers.
    \end{templateoptions}
  \end{element}

  \begin{element}{itemize item}\yes\yes\yes
    \colorfontparents{item}
    This template (with |item| instead of |items|) governs how the
    marker in front of a first-level item is typeset. ``First-level''
    refers to the level of nesting. See the |itemize items| template
    for the \meta{options} that may be given.

    When the template is inserted, the \beamer-font and -color
    |itemize item| is installed. Typically, the font is ignored by the
    template as some special symbol is drawn anyway, by the font may
    be important if an optional argument is given to the
    |\item| command as in |\item[First]|.

    The font and color inherit from the |item| font and color, which
    are explained at the end of this section.
  \end{element}

  \begin{element}{itemize subitem}\yes\yes\yes
    \colorfontparents{subitem}
    Like |itemize item|, only for second-level items. An
    item of an itemize inside an enumerate counts a second-level item.
  \end{element}

  \begin{element}{itemize subsubitem}\yes\yes\yes
    \colorfontparents{subsubitem}
    Like |itemize item|, only for third-level items.
  \end{element}
\end{environment}




\begin{environment}{{enumerate}\opt{|[<|\meta{default overlay specification}|>]|}\oarg{mini template}} 
  Used to display a list of items that are ordered.  Inside the
  environment, use an |\item| command for each topic. By default,
  before each item increasing Arabic numbers  followed by a dot are
  printed (as in ``1.'' and ``2.''). This can be changed by specifying
  a different template,  see below.

  The first optional argument \meta{default overlay specification} has
  exactly the same effect as for the |itemize| environment. It is
  ``detected'' by the opening |<|-sign in the \meta{default overlay
    specification}. Thus, if there is only one optional argument and
  if this argument does not start with |<|, then it is considered to
  be a \meta{mini template}. 

  The syntax of the \meta{mini template} is the same as
  the syntax of mini templates in the |enumerate| package (you do not
  need to include the 
  |enumerate| package, this is done automatically). Roughly spoken,
  the text of the \meta{mini template} is printed before each item,
  but any occurrence of a |1| in the mini template is replaced by the
  current item number, an occurrence of the letter |A| is replaced by
  the $i$th letter of the alphabet (in uppercase) for the $i$th item,
  and the letters |a|, |i|, and |I| are replaced by the corresponding
  lowercase letters, lowercase Roman letters, and uppercase Roman
  letters, respectively. So the mini template |(i)| would yield the
  items (i), (ii), (iii), (iv), and so on. The mini template |A.)|
  would yield the items A.), B.), C.), D.) and so on. For more details
  on the possible mini templates, see the documentation of the
  |enumerate| package. Note that there is also a template that governs
  the appearance of the mini template.
  
  \example
\begin{verbatim}
\begin{enumerate}
\item This is important.
\item This is also important.
\end{enumerate}

\begin{enumerate}[(i)]
\item First Roman point.
\item Second Roman point.
\end{enumerate}

\begin{enumerate}[<+->][(i)]
\item First Roman point.
\item Second Roman point, uncovered on second slide.
\end{enumerate}
\end{verbatim}

  \articlenote
  To use the \meta{mini template}, you have to include the package
  |enumerate|.  

  \lyxnote
  The same constraints as for |itemize| apply.
  
  \begin{element}{enumerate items}\semiyes\no\no
    Similar to |itemize items|, this template is a parent template,
    whose children are |enumerate item|, |enumerate subitem|,
    |enumerate subsubitem|, and |enumerate mini template|. These
    templates govern how the text (the number) of an enumeration is
    typeset. 
    
    \begin{templateoptions}
      \itemoption{default}{}
      The default enumeration marker uses the scheme 1., 2., 3.\ for
      the first level, 1.1, 1.2, 1.3 for the second level and 1.1.1,
      1.1.2, 1.1.3 for the third level. 
      \itemoption{circle}{}
      Places the numbers inside little circles. The colors are taken
      from |item projected| or |subitem projected| or
      |subsubitem projected|.
      \itemoption{square}{}
      Places the numbers on little squares.
      \itemoption{ball}{}
      ``Projects'' the numbers onto little balls.
    \end{templateoptions}
  \end{element}

  \begin{element}{enumerate item}\yes\yes\yes
    This template governs how the number in front of a first-level
    item is typeset. The level here refers to the level of enumeration
    nesting only. Thus an enumerate inside an itemize is a first-level
    enumerate (but it uses the second-level
    |itemize/enumerate body|). 

    When the template is inserted, the \beamer-font and -color
    |enumerate item| are installed.

    The following command is useful for this template:
    \begin{templateinserts}
      \iteminsert{\insertenumlabel}
      inserts the current number of the top-level enumeration (as an
      Arabic number). This insert is also available in the next two
      templates. 
    \end{templateinserts}
  \end{element}

  \begin{element}{enumerate subitem}\yes\yes\yes
    Like |enumerate item|, only for second-level items. 

    \begin{templateinserts}
      \iteminsert{\insertsubenumlabel}
      inserts the current number of the second-level enumeration (as an
      Arabic number). 
    \end{templateinserts}

    \example
\begin{verbatim}
\setbeamertemplate{enumerate subitem}{\insertenumlabel-\insertsubenumlabel}
\end{verbatim}
  \end{element}

  \begin{element}{enumerate subsubitem}\yes\yes\yes
    Like |enumerate item|, only for third-level items. 

    \begin{templateinserts}
      \iteminsert{\insertsubsubenumlabel}
      inserts the current number of the second-level enumeration (as an
      Arabic number). 
    \end{templateinserts}
  \end{element}

  \begin{element}{enumerate mini template}\yes\yes\yes
    This template is used to typeset the number that arises from a
    mini template.

    \begin{templateinserts}
      \iteminsert{\insertenumlabel}
      inserts the current number rendered by this mini template. For
      example, if the \meta{mini template} is |(i)| and this command
      is used in the fourth item, |\insertenumlabel| would yield
      |(iv)|.
    \end{templateinserts}
  \end{element}
\end{environment}

The following templates govern how the \emph{body} of an |itemize| or
an |enumerate| is typeset.
\begin{element}{itemize/enumerate body begin}\yes\no\no
  This template is inserted at the beginning of a first-level
  |itemize| or |enumerate| environment. Furthermore, before this
  template is inserted, the \beamer-font and -color
  |itemize/enumerate body| is used.
\end{element}
\begin{element}{itemize/enumerate body end}\yes\no\no
  This template is inserted at the end of a first-level
  |itemize| or |enumerate| environment.
\end{element}
There exist corresponding templates like
|itemize/enumerate subbody being| from second- and third-level itemize
or enumerates.

\begin{element}{items}\semiyes\no\no
  This template is a parent template of |itemize items| and
  |enumerate items|.
  \example |\setbeamertemplate{items}[circle]| will cause all items in
  |itemize| or |enumerate| environments to become circles (of the
  appropriate size, color, and font).
\end{element}


\label{section-descriptions}
  
\begin{environment}{{description}\opt{|[<|\meta{default overlay specification}|>]|}\oarg{long text}} 
  Like |itemize|, but used to display a list that explains or defines
  labels. The width of \meta{long text} is used to set the
  indentation. Normally, you choose the widest label in the
  description and copy it here. If you do not give this argument, the
  default width is used, which can be changed using |\setbeamersize|
  with the argument |description width=|\meta{width}.

  As for |enumerate|, the \meta{default overlay specification} is
  detected by an opening~|<|. The effect is the same as for
  |enumerate| and |itemize|.
  \example
\begin{verbatim}
\begin{description}
\item[Lion] King of the savanna.
\item[Tiger] King of the jungle.
\end{description}

\begin{description}[longest label]
\item<1->[short] Some text.
\item<2->[longest label] Some text.
\item<3->[long label] Some text.
\end{description}
\end{verbatim}

  \example The following has the same effect as the previous example:
\begin{verbatim}
\begin{description}[<+->][longest label]
\item[short] Some text.
\item[longest label] Some text.
\item[long label] Some text.
\end{description}
\end{verbatim}

  \lyxnote
  Since you cannot specify the optional argument in \LyX, if you wish
  to specify the width, you may wish to use the following command
  shortly before the environment:

  |\setbeamersize{description width of={|\marg{text}|}}|

  \example
\begin{verbatim}
\setbeamersize{description width of={longest label}}
\begin{description}
\item<1->[short] Some text.
\item<2->[longest label] Some text.
\item<3->[long label] Some text.
\end{description}
\end{verbatim}
  
  \begin{element}{description item}\yes\yes\yes
    This template is used to typeset the description items. When this
    template is called, the \beamer-font and -color |description item|
    are installed.
    
    \begin{templateoptions}
      \itemoption{default}{}
      By default, the description item text is just inserted without
      any modification.
    \end{templateoptions}

    The main insert that is useful inside this template is:
    \begin{templateinserts}
      \iteminsert{\insertdescriptionitem} inserts the text of the
      current description item.
    \end{templateinserts}
  \end{element}
\end{environment}



In order to simplify changing the color or font of items, the
different kinds of items inherit form or just use the following
``general'' \beamer-color and fonts:

\begin{element}{item}\no\yes\yes
  \colorparents{local structure}
  \fontparents{structure}

  This color/font serves as a parent for the individual items of
  |itemize| and |enumerate| environments, but also for items in the
  table of contents. Since its color parent is the |local structure|,
  a change of that color causes the color of items to change
  accordingly.
\end{element}

\begin{element}{item projected}\no\yes\yes
  \colorfontparents{item}

  This is a special ``version'' of the |item| color and font that
  should be used by templates that render items with text (as in an
  enumeration) and which to ``project'' this text onto something like
  a ball or a square or whatever. While the normal |item| color
  typically has a transparent background, the |item projected|
  typically has a colored background and, say, a white foreground. 
\end{element}

\begin{element}{subitem}\no\yes\yes
  \colorfontparents{item}
  Same as |item| for subitems, that is, for items on the second level of
  indentation. 
\end{element}

\begin{element}{subitem projected}\no\yes\yes
  \colorfontparents{item projected}
  Same as |item projected| for subitems, that is, for items on the
  second level of indentation. 
\end{element}

\begin{element}{subsubitem}\no\yes\yes
  \colorfontparents{subitem}
\end{element}

\begin{element}{subsubitem projected}\no\yes\yes
  \colorfontparents{subitem projected}
\end{element}




\subsection{Hilighting}

The \beamer\ class predefines commands and environments for
hilighting text. Using these commands makes is easy to change the
appearance of a document by changing the theme. 


\begin{command}{\structure\sarg{overlay specification}\marg{text}}
  The given text is marked as part of the structure, that is, it is
  supposed to help the audience see the structure of your
  presentation. If the \meta{overlay specification} is present, the
  command only has an effect on the specified slides.
  \example|\structure{Paragraph Heading.}|

  Internally, this command just puts the \emph{text} inside a
  |structureenv| environment.
 
  \articlenote
  Structure text is typeset as bold text. This can be changed by
  modifying the templates.

  \lyxnote
  You need to use \TeX-mode to insert this command.

  \begin{element}{structure}\no\yes\yes
    This color/font is used when structured text is typeset, but it is
    also widely used as a base for many other colors including the
    headings of blocks, item buttons, and titles. In most color
    themes, the colors for navigational elements in the headline or
    the footline are derived from the foreground color of
    |structure|. By changing the structure color you can easily change
    the ``basic color'' of your presentation, other than the color of
    normal text. See also the related color |local structure| and the
    related font |tiny structure|.
    
    Inside the |\structure| command, the background of the color is
    ignored, but this is not necessarily true for elements that
    inherit their color from |structure|. There is no template
    |structure|, use |structure begin| and |structure end| instead.
  \end{element}
 
  \begin{element}{local structure}\no\yes\no
    This color should be used to typeset structural elements that change
    their color according to the ``local environment.'' For example, the
    color of an item ``button'' in an |itemize| environment changes its
    color according to circumstances. If it is used inside an example
    block, it should have the |example text| color; if it is currently
    ``alerted'' it should have the |alerted text| color. This color
    will setup by certain environments to have the color that should be
    used to typset things like item buttons. Since the color used for
    items, |item|, inherits from this color by default, items
    automatically change their color according to the current
    situation.

    If you write your own environment in which the item buttons are
    similar structural elements should have a different color, you
    should change the color |local structure| inside these
    environments. 
  \end{element}
  
  \begin{element}{tiny structure}\no\no\yes
    This special font is used for ``tiny'' structural text. Basically,
    this font should be used whenever a structural element uses a tiny
    font. The idea is that the tiny versions of the |structure| font
    often are not suitable. For example, it is often necessary to use a
    boldface version for them. Also, one might wish to have serif smallcaps
    structural text, but still retain normal sans-serif tiny structural
    text.
  \end{element}
\end{command}

\begin{environment}{{structureenv}\sarg{overlay specification}}
  Environment version of the |\structure| command.

  \begin{element}{structure begin}\yes\no\no
    This text is inserted at the beginning of a |structureenv|
    environment.

    \begin{templateoptions}
      \itemoption{default}{}

      \articlenote
      The text is typeset in boldface.
    \end{templateoptions}
  \end{element}

  \begin{element}{structure end}\yes\no\no
    This text is inserted at the end of a |structureenv| environment.
  \end{element}
\end{environment}


\begin{command}{\alert\sarg{overlay specification}\marg{hilighted text}}
  The given text is hilighted, typically by coloring the text red. If
  the \meta{overlay specification} is present, the command only has an
  effect on the specified slides.
  \example |This is \alert{important}.|

  Internally, this command just puts the \emph{hilighted text} inside
  an |alertenv|.
  
  \articlenote
  Alerted text is typeset as emphasized text. This can be changed by
  modifying the templates, see below.

  \lyxnote
  You need to use \TeX-mode to insert this command (which is not very
  convenient).

  \begin{element}{alerted text}\no\yes\yes
    This color/font is used when alerted text is typeset. The
    background is currently ignored. There is no template
    |alerted text|, rather there are templates |alerted text begin|
    and |alerted text end| that are inserted before and after alerted
    text.
  \end{element}
\end{command}

\begin{environment}{{alertenv}\sarg{overlay specification}}
  Environment version of the |\alert| command.

  \begin{element}{alerted text begin}\yes\no\no
    This text is inserted at the beginning of a an |alertenv|
    environment.

    \begin{templateoptions}
      \itemoption{default}{}

      \beamernote
      This changes the color |local structure| to |alerted text|. This
      causes things like buttons or items to be colored in the same
      color as the alerted text, which is often visually pleasing. See
      also the |\structure| command.

      \articlenote
      The text is emphasized.
    \end{templateoptions}
  \end{element}

  \begin{element}{alerted text end}\yes\no\no
    This text is inserted at the end of an |alertenv| environment.
  \end{element}
\end{environment}




\subsection{Block Environments}
\label{predefined}

The \beamer\ class predefines an environment for typesetting a
``block'' of text that has a heading. The appearance of blocks can
easily be changed using the following template:

\begin{element}{blocks}\semiyes\no\no
  Changining this parent template changes the templates of normal
  blocks, alerted blocks, and example blocks.

  \example |\setbeamertemplate{blocks}[default]|
  \example |\setbeamertemplate{blocks}[rounded][shadow=true]|

  \begin{templateoptions}
    \itemoption{default}{}
    The default setting typesets the block title on its own line. If a
    background is specified either for the |block title| or for the
    |block body|, this background color is used as background of the
    title or body, respectively. For alerted and example blocks, the
    corresponding \beamer-colors and -fonts are used, instead.
    \itemoption{rounded}{\oarg{shadow=true}}
    Makes the blocks ``rounded.'' This means that the corners of the
    backgrounds of the blocks are ``rounded off.'' If the
    |shadow=true| option is given, a ``shadow'' is drawn behind the
    block. 
  \end{templateoptions}
\end{element}


\begin{environment}{{block}\sarg{action specification}\marg{block
      title}\sarg{action specification}}
  Only one \meta{action specification} may be given.
  Inserts a block, like a definition or a theorem, with the title
  \meta{block title}. If the \meta{action specification} is present,
  the given actions are taken on the specified slides, see
  Section~\ref{section-action-specifications}. In the example, the 
  definition is shown only from slide 3 onward.
  \example
\begin{verbatim}
  \begin{block}<3->{Definition}
    A \alert{set} consists of elements.
  \end{block}
\end{verbatim}

  \articlenote
  The block name is typeset in bold.

  \lyxnote
  The argument of the block must (currently) be given in
  \TeX-mode. More precisely, there must be an opening brace in
  \TeX-mode and a closing brace in \TeX-mode around it. The text
  in between can also be typeset using \LyX. I hope to get rid of this
  some day.

  \begin{element}{block begin}\yes\no\no
    This template is inserted at the beginning of a block before the
    \meta{environment contents}. Inside this
    template, the block title can be accessed via the following
    insert:
    \begin{itemize}
      \iteminsert{\insertblocktitle}
      Inserts the \meta{block title} into the template.
    \end{itemize}

    When the template starts, no special color or font is installed
    (for somewhat complicated reasons). Thus, this template should
    install the correct colors and fonts for the title and the body itself.
  \end{element}

  \begin{element}{block end}\yes\no\no
    This template is inserted at the end of a block.
  \end{element}

  \begin{element}{block title}\no\yes\yes
    This \beamer-color/-font should be used to typeset the title of
    the block. Since neither the color nor the font are setup
    automatically, the template |block begin| must do so itself.

    The default block template and also the |rounded| version honor
    the background of this color.
  \end{element}

  \begin{element}{block body}\no\yes\yes
    This \beamer-color/-font should be used to typeset the body of the
    block, that is, the \meta{environment contents}. As for
    |block title|, the color and font must be setup by the template
    |block begin|.
  \end{element}
\end{environment}


\begin{environment}{{alertblock}\sarg{action specification}\marg{block
title}\sarg{action specification}} 
  Inserts a block whose title is hilighted. Behaves like the |block|
  environment otherwise.
  \example
\begin{verbatim}
  \begin{alertblock}{Wrong Theorem}
    $1=2$.
  \end{alertblock}
\end{verbatim}

  \articlenote
  The block name is typeset in bold and is emphasized.

  \lyxnote
  Same applies as for |block|.

  \begin{element}{block alerted begin}\yes\no\no
    Same applies as for normal blocks.
  \end{element}

  \begin{element}{block alerted end}\yes\no\no
    Same applies as for normal blocks.
  \end{element}

  \begin{element}{block title alerted}\no\yes\yes
    Same applies as for normal blocks.
  \end{element}

  \begin{element}{block body alerted}\no\yes\yes
    Same applies as for normal blocks.
  \end{element}
\end{environment}

\begin{environment}{{exampleblock}\sarg{action
specification}\marg{block title}\sarg{overlay specification}} 
  Inserts a block that is supposed to be an example. Behaves like the
  |block| environment otherwise.
  
  \example In the following example, the block is completely
  suppressed on the first slide (it does not even occupy any space).
\begin{verbatim}
  \begin{exampleblock}{Example}<only@2->
    The set $\{1,2,3,5\}$ has four elements.
  \end{exampleblock}
\end{verbatim}

  \articlenote
  The block name is typeset in italics.

  \lyxnote
  Same applies as for |block|.

  \begin{element}{block example begin}\yes\no\no
    Same applies as for normal blocks.
  \end{element}

  \begin{element}{block example end}\yes\no\no
    Same applies as for normal blocks.
  \end{element}

  \begin{element}{block title example}\no\yes\yes
    Same applies as for normal blocks.
  \end{element}

  \begin{element}{block body example}\no\yes\yes
    Same applies as for normal blocks.
  \end{element}
\end{environment}

\lyxnote
Overlay specifications must be given right at the beginning of the
environments and in \TeX-mode.



\subsection{Theorem Environments}
\label{section-theorems}

The \beamer\ class predefines several environments, like |theorem| or
|definition| or |proof|, that you can use to typeset things like,
well, theorems, definitions, or proofs. The complete list is the
following:  |theorem|, |corollary|, |definition|,
|definitions|, |fact|, |example|, and |examples|. The following German
block environments are also predefined: |Problem|, |Loesung|,
|Definition|, |Satz|, |Beweis|, |Folgerung|, |Lemma|, |Fakt|,
|Beispiel|, and |Beispiele|.

Here is a typical example on how to use them:

\begin{verbatim}
\begin{frame}
  \frametitle{A Theorem on Infinite Sets}

  \begin{theorem}<1->
    There exists an infinite set.
  \end{theorem}

  \begin{proof}<2->
    This follows from the axiom of infinity.
  \end{proof}

  \begin{example}<3->[Natural Numbers]
    The set of natural numbers is infinite.
  \end{example}
\end{frame}
\end{verbatim}

In the following, only the English versions are discussed. The German
ones behave  analogously.

\begin{environment}{{theorem}\sarg{action
  specification}\oarg{additional text}\sarg{action specification}}
  Inserts a theorem. Only one \meta{action specification} may be
  given. If present, the \meta{additional text} is shown behind the
  word ``Theorem'' in rounded brackets (although this can be changed by
  the template).

  The appearance of the theorem is governed by the templates
  |theorem begin| and |theorem end|, see their description later on
  for details on how to change these. Every theorem is put into a
  |block| environment, thus the templates for blocks also apply.

  The theorem style (a concept from |amsthm|) used for this
  environment is |plain|. In this style, the body of a theorem should
  be typeset in italics. The head of the theorem should be typeset in
  a bold font, but this is usually overruled by the templates.

  If the option |envcountsect| is given either as class option in one
  of the |presentation| modes or as an option to the package
  |beamerarticle| in |article| mode, then the numbering of the
  theorems is local to each section with the section number prefixing
  the theorem number; otherwise they are numbered consecutively
  throughout the presentation or article. I recommend using this
  option in |article| mode.

  By default, no theorem numbers are shown in the |presentation| modes.

  \example
\begin{verbatim}
\begin{theorem}[Kummer, 1992]
  If $\#^_A^n$ is $n$-enumerable, then $A$ is recursive.
\end{theorem}

\begin{theorem}<2->[Tantau, 2002]
  If $\#_A^2$ is $2$-fa-enumerable, then $A$ is regular.
\end{theorem}
\end{verbatim}

  \lyxnote
  If present, the optional argument and the action specification must
  be given in \TeX-mode at the beginning of the environment.
\end{environment}

The environments \declare{|corollary|}, \declare{|fact|}, and
\declare{|lemma|} behave exactly the same way.

\begin{classoption}{envcountsect}
  Causes theorems, definitions, and so on to be numbered locally to
  each section. Thus, the first theorem of the second section would be
  Theorem~2.1 (assuming that there are no definitions, lemmas, or
  corollaries earlier in the section).
\end{classoption}

\begin{environment}{{definition}\sarg{action
      specification}\oarg{additional text}\sarg{action specification}}
  Behaves like the |theorem| environment, except that the theorem
  style |definition| is used. In this style, the body of a theorem is
  typeset in an upright font.
\end{environment}

The environment \declare{|definitions|} behaves exactly the same way.

\begin{environment}{{example}\sarg{action
      specification}\oarg{additional text}\sarg{action specification}}
  Behaves like the |theorem| environment, except that the theorem
  style |example| is used. A side-effect of using this theorem style
  is that the \meta{environment contents} is put in an |exampleblock|
  instead of a |block|.
\end{environment}

The environment \declare{|examples|} behaves exactly the same way.

\beamernote
The default template for typesetting theorems suppresses the theorem
number, even if this number is ``available'' for typesetting (which it
is by default in all predefined environments; but if you define your
own environment using |\newtheorem*| no number will be available).

\articlenote
In |article| mode, theorems are automatically numbered. By specifying
the class option |envcountsect|, theorems will be numbered locally to each
section, which is usually a good idea, except for very short
articles.

\begin{environment}{{proof}\sarg{action specification}\oarg{proof
name}\sarg{action specification}}
  Typesets a proof. If the optional \meta{proof name} is given, it
  completely replaces the word ``Proof.'' This is different from
  normal theorems, where the optional argument is shown in brackets.

  At the end of the theorem, a |\qed| symbol is shown, except if you
  say |\qedhere| earlier in the proof (this is exactly as in
  |amsthm|). The default |\qed| symbol is an open rectangle. To
  completely suppress the symbol, write |\def\qedsymbol{}| in 
  your preamble. To get an closed rectangle, say
\begin{verbatim}
\setbeamertemplate{qed symbol}{\vrule width1.5ex height1.5ex depth0pt}
\end{verbatim}

  If you use |babel| and a different language, the text ``Proof'' is
  replaced by whatever is appropriate in the selected language.

  \example
\begin{verbatim}
\begin{proof}<2->[Sketch of proof]
  Suppose ...
\end{proof}
\end{verbatim}

  \begin{element}{qed symbol}\yes\yes\yes
    The symbol is shown at the end of every proof.
  \end{element}
\end{environment}

You can define new environments using the following command:

\begin{command}{\newtheorem\opt{|*|}\marg{environment name}\oarg{numbered same
      as}\marg{head text}\oarg{number within}}
  This command is used exactly the same way as in the |amsthm| package
  (as a matter of fact, it is the command from that package), see its
  documentation. The only difference is that environments declared using
  this command are overlay-specification-aware in \beamer\ and that,
  when typeset, are typeset according to \beamer's templates.

  \articlenote
  Environments declared using this command are also
  overlay-specification-aware in |article| mode.

  \example |\newtheorem{observation}[theorem]{Observation}|
\end{command}

You can also use |amsthm|'s command |\newtheoremstyle| to define new
theorem styles. Note that the default template for theorems will
ignore any head font setting, but will honor the body font setting.

If you wish to define the environments like |theorem| differently (for
example, have it numbered within each subsection), you can use the
following class option to disable the definition of the predefined
environments: 

\begin{classoption}{notheorems}
  Switches off the definition of default blocks like |theorem|, but
  still loads |amsthm| and makes theorems  
  overlay-specificiation-aware.
\end{classoption}

The option is also available as a package option for
|beamerarticle| and has the same effect.

\articlenote
In the |article| version, the package |amsthm| sometimes clashes with
the document class. In this case you can use the following option,
which is once more available as a class option for \beamer\ and as a
package option for |beamerarticle|, to switch off the loading of
|amsthm| altogether. 

\begin{classoption}{noamsthm}
  Does not load |amsthm| and also not |amsmath|. Environments like
  |theorem| or |proof| will not be available.
\end{classoption}



\begin{element}{theorems}\semiyes\no\no
  This template is a parent of |theorem begin| and |theorem end|, see
  the first for a detailed discussion of how the theorem templates are
  set.

  \example |\setbeamertemplate{theorems}[numbered]|
  
  \begin{templateoptions}
    \itemoption{default}{}
    By default, theorems are typeset as follows: The font specification for
    the body is honored, the font specification for the head is
    ignored. No theorem number is printed.
    \itemoption{normal font}{}
    Like the default, except all font specifications for the body are
    ignored. Thus, the fonts are used that are normally used for
    blocks.
    \itemoption{numbered}{}
    This option is like the default, except that the theorem
    number is printed for environments that are numbered.
    \itemoption{ams style}{}
    This causes theorems to be put in a |block| or |exampleblock|, but
    to be otherwise typeset as is normally done in |amsthm|. Thus the
    head font and body font depend on the setting for the theorem to be
    typeset and theorems are numbered.
  \end{templateoptions}
\end{element}


\begin{element}{theorem begin}\yes\no\no
  Whenever an environment declared using the command |\newtheorem| is
  to be typeset, this template is inserted at the beginning and the
  template |theorem end| at the end. If there is a overlay
  specification when an environment like |theorem| is 
  used, this overlay specification will directly follow the
  \meta{block beginning template} upon invocation. This is even true
  if there was an optional argument to the |theorem| environment. This
  optional argument is available via the insert |\inserttheoremaddition|.

  Numerous inserts are available in this template, see below.  

  Before the template starts, the font is set to the body font
  prescribed by the environment to be typeset.
  
  \example The following typesets theorems like |amsthm|:
\begin{verbatim}
\setbeamertemplate{theorem begin}
{%
  \begin{\inserttheoremblockenv}
  {%
    \inserttheoremheadfont
    \inserttheoremname
    \inserttheoremnumber
    \ifx\inserttheoremaddition\@empty\else\ (\inserttheoremaddition)\fi%
    \inserttheorempunctuation
  }%
}
\setbeamertemplate{theorem end}{\end{\inserttheoremblockenv}}
\end{verbatim}

  \example In the following example, all font ``suggestions'' for the
  environment are suppressed or ignored; and the theorem number is
  suppressed.
\begin{verbatim}
\setbeamertemplate{theorem begin}
{%
  \normalfont% ignore body font
  \begin{\inserttheoremblockenv}
  {%
    \inserttheoremname
    \ifx\inserttheoremaddition\@empty\else\ (\inserttheoremaddition)\fi%
  }%
}
\setbeamertemplate{theorem end}{\end{\inserttheoremblockenv}}
\end{verbatim}

  The following inserts are available inside this template:
  \begin{itemize}
    \iteminsert{\inserttheoremblockenv}
    This will normally expand to |block|, but if a theorem that has
    theorem style |example| is typeset, it will expand to
    |exampleblock|. Thus you can use this insert to decide which
    environment should be used when typesetting the theorem.

    \iteminsert{\inserttheoremheadfont}
    This will expand to a font changing command that switches to the
    font to be used in the head of the theorem. By not inserting it, you
    can ignore the head font.

    \iteminsert{\inserttheoremname}
    This will expand to the name of the environment to be typeset (like
    ``Theorem'' or ``Corollary''). 

    \iteminsert{\inserttheoremnumber}
    This will expand to the number of the current theorem preceeded by a
    space or to nothing, if the current theorem does not have a number.

    \iteminsert{\inserttheoremaddition}
    This will expand to the optional argument given to the environment
    or will be empty, if there was no optional argument.

    \iteminsert{\inserttheorempunctuation}
    This will expand to the punctuation character for the current
    environment. This is usually a period.
  \end{itemize}
\end{element}

\begin{element}{theorem end}\yes\no\no
  Inserted at the end of a theorem.
\end{element}



\subsection{Framed and Boxed Text}

In order to draw a frame (a rectangle) around some text, you can use
\LaTeX s standard command |\fbox| and also |\frame| (inside a \beamer\
frame, the |\frame| command changes its meaning to the normal \LaTeX\
|\frame| command). More frame types are offered by the
package |fancybox|, which defines the following commands:
|\shadowbox|, |\doublebox|, |\ovalbox|, and |\Ovalbox|. Please consult
the \LaTeX\ Companion for details on how to use these commands.

The \beamer\ class also defines two environments for creating coloured
boxes.

\begin{environment}{{beamercolorbox}\oarg{options}\marg{beamer color}}
  This environment can be used to conveniently typeset some text using
  some \beamer-color. Basically, the following two command blocks do
  the same: 
\begin{verbatim}
\begin{beamercolorbox}{beamer color}
  Text
\end{beamercolorbox}

{
  \usebeamercolor{beamer color}
  \colorbox{bg}{
    \color{fg}
    Text
  }
}
\end{verbatim}
  In other words, the environment installs the \meta{beamer color} and
  uses the background for the background of the box and the foreground
  for the text inside the box. However, in reality, numerous
  \meta{options} can be given to specify in much greater detail how
  the box is rendered.

  If the background color of \meta{beamer color} is empty, no
  background is drawn behind the text, that is, the background is
  ``transparent.''

  This command is used extensively by the default inner and outer
  themes for typesetting the headlines and footlines. It is not really
  intended to be used in normal frames (for example, it is not
  available inside |article| mode). You should prefer using
  structuring elements like blocks or theorems that automatically
  insert colored boxes as needed.

  \example The following example could be used to typeset a headline
  with two lines, the first showing the document title, the second
  showing the author's name:
\begin{verbatim}
\begin{beamercolorbox}[ht=2.5ex,dp=1ex,center]{title in head/foot}
  \usebeamerfont{title in head/foot}
  \insertshorttitle
\end{beamercolorbox}%
\begin{beamercolorbox}[ht=2.5ex,dp=1ex,center]{author in head/foot}
  \usebeamerfont{author in head/foot}
  \insertshortauthor
\end{beamercolorbox}
\end{verbatim}

  \example Typesetting a postit:
\begin{verbatim}
\setbeamercolor{postit}{fg=black,bg=yellow}
\begin{beamercolorbox}[sep=1em,wd=5cm]{postit}
  Place me somewhere!
\end{beamercolorbox}
\end{verbatim}

  
  The following \meta{options} can be given:
  \begin{itemize}
  \item \declare{|wd=|\marg{width}} sets the width of the box. This
    command has two effects: First, \TeX's |\hsize| is set to
    \meta{width}. Second, after the box has been typeset, its width is
    set to \meta{width} (no matter what it actually turned out to
    be). Since setting the |\hsize| does not automatically change some
    of \LaTeX's linewidth dimensions, you should consider using a
    minipage inside this environment if you fool around with the
    width.

    If the width is larger than the normal text width, as specified by
    the value of |\textwidth|, the width of the resulting box is reset
    to the width |\textwidth|, but intelligent negative skips are
    inserted at the left and right end of the box. The net effect of
    this is that you can use a width larger than the text width for a
    box and can insert the resulting box directly into normal text
    without getting annoying warnings and having the box positioned
    sensibly.
  \item \declare{|dp=|\marg{depth}} sets the depth of the box,
    overriding the real depth of the box. The box is first typeset
    normally, then the depth is changed afterwards. This option is
    useful for creating boxes that have guaranteed size.

    If the option is not given, the box has its ``natural'' depth,
    which results from the typesetting. For example, a box containing
    only the letter ``a'' will have a different depth from a box
    containing only the letter ``g.''
  \item \declare{|ht=|\meta{height}} sets the height of the box,
    overriding the real height. Note that the ``height'' does not
    include the depth (see, for example, the \TeX-book for
    details). If you want a one-line box that always has the same
    size, setting the height to 2.25ex and the depth to 1ex is usually
    a good option.
  \item \declare{|left|} causes the text inside the box to be typeset
    left-aligned and with a (radically) ragged right border. This is
    the default. To get a better ragged right border, use the
    |rightskip| option. 
  \item \declare{|right|} causes the text to be right-aligned with a
    (radically) ragged left border.
  \item \declare{|center|} centers the text inside the box.
  \item \declare{|leftskip=|\meta{left skip}} installs the \meta{left
      skip} inside the box as the left skip. \TeX's left skip is a
    glue that is inserted at the left end of every line. See the
    \TeX-book for details.
  \item \declare{|rightskip=|\meta{right skip}} install the
    \meta{right skip}. To get a good ragged right border, try, say,
    |\rightskip=0pt plus 4em|.
  \item \declare{|sep=|\meta{dimension}} sets the size of extra
    space around the text. This space is added ``inside the box,''
    which means that if you specify a |sep| of 1cm and insert the box
    normally into the vertical list, then the left border of the box
    will be aligned with the left border of the slide text, while the
    left border of the text inside the box will be 1cm to the right of
    this left border. Likewise, the text inside the box will stop 1cm
    before the right border of the normal text.
  \item \declare{|colsep=|\meta{dimension}} sets the extra ``color
    separation space'' around the text. This space behaves the
    same way as the space added by |sep|, only this space is only
    inserted if the box has a colored background, that is, if the
    background of the \meta{beamer color} is not empty. This command
    can be used together with |sep|, the effects accumulate.
  \item \declare{|colsep*=|\meta{dimension}} sets an extra color
    separation space around the text that is \emph{horizontally
    outside the box}. This means that if the box has a background,
    this background will protrude by \meta{dimension} to the left and
    right of the text, but this protruding background will not be
    taken intro consideration by \TeX\ for typesetting purposes.

    A typical example usage of this option arises when you insert a
    box with a coloured background in the middle of normal text. In
    this case, if the background color is set, you would like a
    background to be drawn behind the text \emph{and} you would like a
    certain extra space around this text (the background should not
    stop immediately at the borders of the text, this looks silly)
    \emph{and} you would like the normal text always to be at the same 
    horizontal position, independently of whether a background is
    present or not. In this case, using |colsep*=4pt| is a good
    option.
  \item \declare{|shadow|}\opt{|=|\meta{true or false}} draws a shadow
    behind the box. Currently, this option only has an effect if
    used together with the |rounded| option, but that may change.
  \item \declare{|rounded|}\opt{|=|\meta{true or false}} causes the
    borders of the box to be rounded off if there is a background
    installed. This command internally calls |beamerboxesrounded|.
  \item \declare{|ignorebg|} causes the background color of the
    \meta{beamer color} to be ignored, that is, to be treated as if it
    were set to ``transparent'' or ``empty.''
  \item \declare{vmode} causes \TeX\ to be in vertical mode when the
    box starts. Normally, \TeX\ will be in horizontal mode at the
    start of the box (a |\leavevmode| is inserted automatically at the
    beginning of the box unless this option is given). Only
    \TeX perts need this option, so, if you use it, you will
    probably know what you are doing anyway.
  \end{itemize}
\end{environment}


\begin{environment}{{beamerboxesrounded}\oarg{options}\marg{head}}
  The text inside the environment is framed by a rectangular area with
  rounded corners. For the large rectangular area, the \beamer-color
  specified with the |lower| option  is used. Its background is used
  for the background, its foreground for the foreground. If the
  \meta{head} is not empty, \meta{head} is drawn in the 
  upper part of the box using the \beamer-color specified with the
  |upper| option for the fore- and background. The following options
  can be given: 
  \begin{itemize}
  \item \declare{|lower=|\meta{beamer color}} sets the \beamer-color
    to be used for the lower (main) part of the box. Its background is
    used for the background, its foreground for the foreground of the
    main part of the box. If either is empty, the current background
    or foreground is used. The box will never be transparent.
  \item \declare{|upper=|\meta{beamer color}} sets the \beamer-color
    used for the upper (head) part of the box. It is only used if the
    \meta{head} is not empty.     
  \item \declare{|width=|\meta{dimension}} causes the width of the
    text inside the box to be the specified \meta{dimension}. By
    default, the |\textwidth| is used. Note that the box will protrude
    4pt to the left and right.
  \item \declare{|shadow=|\meta{true or false}}. If set to |true|, a
    shadow will be drawn.    
  \end{itemize}
  If no \meta{head} is given, the head part is completely suppressed.
  \example
\begin{verbatim}
\begin{beamerboxesrounded}[upper=block head,lower=block body,shadow=true]{Theorem}
  $A = B$.
\end{beamerboxesrounded}
\end{verbatim}

  \articlenote
  This environment is not available in |article| mode.
\end{environment}





\subsection{Figures and Tables}

You can use the standard \LaTeX\ environments |figure| and
|table| much the same way you would normally use them. However,
any placement specification will be ignored. Figures and tables are
immediately inserted where the environments start. If there are too
many of them to fit on the frame, you must manually split them among
additional frames or use the |allowframebreaks| option.

\example
\begin{verbatim}
\begin{frame}
  \begin{figure}
    \pgfuseimage{myfigure}
    \caption{This caption is placed below the figure.}
  \end{figure}

  \begin{figure}
    \caption{This caption is placed above the figure.}
    \pgfuseimage{myotherfigure}
  \end{figure}
\end{frame}
\end{verbatim}

\begin{element}{caption}\yes\yes\yes
  This template is used to render the caption.
  \begin{templateoptions}
    \itemoption{default}{}
    typesets the caption name (a word like ``Figure'' or ``Abbildung''
    or ``Table,'' depending on whether a table or figure is typeset
    and depending on the currently installed language) before the
    caption text. No number is printed, since these make little sense
    in a normal presentation.
    \itemoption{numbered}{}
    adds the figure or table number to the caption. Use this option
    only if your audience has a printed handout or printed lecture
    notes that follow the same numbering.
    \itemoption{caption name own line}{}
    As the name suggests, this options puts the caption name (like
    ``Figure'') on its own line.
  \end{templateoptions}

  Inside the template, you can use the following inserts:
  \begin{itemize}
    \iteminsert{\insertcaption}
    Inserts the text of the current caption.

    \iteminsert{\insertcaptionname}
    Inserts the name of the current caption. This word
    is either ``Table'' or ``Figure'' or, if the |babel| package is
    used, some translation thereof.

    \iteminsert{\insertcaptionnumber}
    Inserts the number of the current figure or table.
  \end{itemize}
\end{element}

\begin{element}{caption name}\no\yes\yes
  These \beamer-color and -font are used to typeset the caption name
  (a word like ``Figure''). The |caption| template must directly
  ``use'' them, they are not installed automatically by the
  |\insertcaptionname| command.
\end{element}





\subsection{Splitting a Frame into Multiple Columns}

The \beamer\ class offers several commands and environments for
splitting (perhaps only part of) a frame into multiple columns. These
commands have nothing to do with \LaTeX's commands for creating
columns. Columns are especially useful for placing a graphic next to a
description/explanation.

The main environment for creating columns is called |columns|. Inside
this environment, you can either place several |column| environments,
each of which creates a new column, or use the |\column| command to
create new columns.

\begin{environment}{{columns}\oarg{options}}
  A multi-column area. Inside the environment you should place only
  |column| environments or |\column| commands (see below). The
  following \meta{options} may be given: 
  \begin{itemize}
  \item
    \declare{|b|} will cause the bottom lines of the columns to be
    vertically aligned.
  \item
    \declare{|c|} will cause the columns to be centered vertically
    relative to each other. Default, unless the global option
    |t| is used. 
  \item
    \declare{|onlytextwidth|} is the same as |totalwidth=\textwidth|.
  \item
    \declare{|t|} will cause the first lines of the columns to be
    aligned. Default if global option |t| is used.
  \item
    \declare{|T|} is similar to the |t| option, but |T| aligns the
    tops of the first lines while |t| aligns the so-called baselines
    of the first lines. If strange things seem to happen in
    conjunction with the |t| option (for example if a graphic suddenly
    ``drops down'' with the |t| option instead of ``going up,''), try
    using this option instead.
  \item
    \declare{|totalwidth=|\meta{width}} will cause the columns to occupy
    not the whole page width, but only \meta{width}, all told.
  \end{itemize}
    
  \example
\begin{verbatim}
\begin{columns}[t]
  \begin{column}{5cm}
    Two\\lines.
  \end{column}
  \begin{column}{5cm}
    One line (but aligned).
  \end{column}
\end{columns}
\end{verbatim}
  
  \example
\begin{verbatim}
\begin{columns}[t]
  \column{5cm}
    Two\\lines.

  \column[T]{5cm}
    \includegraphis[height=3cm]{mygraphic.jpg}
\end{columns}
\end{verbatim}

  \articlenote
  This environment is ignored in |article| mode.
  
  \lyxnote
  Use ``Columns'' or ``ColumnsTopAligned'' to create a |columns|
  environment. To pass options, insert them in \TeX-mode right at the
  beginning of the environment in square brackets.
\end{environment}

To create a column, you can either use the |column| environment or the
|\column| command. 

\begin{environment}{{column}\oarg{placement}\marg{column width}}
  Creates a single column of width \meta{column width}. The vertical
  placement of the enclosing |columns| environment can be overruled by
  specifying a specific \meta{placement} (|t| and |T| for the two top
  modes, |c| for centered, and |b| for bottom). 

  \example The following code has the same effect as the above examples:
\begin{verbatim}
\begin{columns}
  \begin{column}[t]{5cm}
    Two\\lines.
  \end{column}
  \begin{column}[t]{5cm}
    One line (but aligned).
  \end{column}
\end{columns}
\end{verbatim}
  \articlenote
  This command is ignored in |article| mode.

  \lyxnote
  The ``Column'' styles insert the command version, see below.
\end{environment}

\begin{command}{{\column}\oarg{placement}\marg{column width}}
  Starts a single column. The parameters and options are the same as
  for the |column| environment. The column automatically ends with the
  next occurrence of |\column| or of a |column| environment or of the
  end of the current |columns| environment.

  \example 
\begin{verbatim}
\begin{columns}
  \column[t]{5cm}
    Two\\lines.
  \column[t]{5cm}
    One line (but aligned).
\end{columns}
\end{verbatim}
  \articlenote
  This command is ignored in |article| mode.

  \lyxnote
  In a ``Column'' style, the width of the column must be given as
  normal text, not in \TeX-mode.
\end{command}



\subsection{Positioning Text and Graphics Absolutely}

Normally, \beamer\ uses \TeX's normal typesetting mechanism to
position text and graphics on the page. In certain situation you may
instead wish a certain text or graphic to appear at a
page position that is specified \emph{absolutely}. This means that the
position is specified relative to the upper left corner of the slide.

The package |textpos| provides several commands for positioning text
absolutely and it works together with \beamer. When using this
package, you will typically have to specify the options |overlay| and
perhaps |absolute|. For details on how to use the package, please see
its documentation.



\subsection{Verbatim and Fragile Text}

If you wish to use a |{verbatim}| environment in a frame, you have to
add the option |[fragile]| to the |{frame}| environment. In this case,
you really have to use the |{frame}| environment (not the |\frame|
command) and the |\end{frame}| must be alone on a single line. Using
this option will cause the frame contents to be written to an external
file and the read back. See the description of the |{frame}|
environment for more details.

You must also use the |[fragile]| option for frames that include any
``fragile'' text, which is any text that is not ``interpreted the way
text is usually interpreted by \TeX.'' For example, if you use a
package that (locally) redefined the meaning of, say, the character
|&|, you must use this option.

Inside |{verbatim}| environments you obviously cannot use commands
like |\alert<2>| to highlight part of code since the text is written
in, well, verbatim. There are several good packages like |alltt| or
|listings| that allow you to circumvent this problem. For simple
cases, the following environment can be used, which is defined by
\beamer:

\begin{environment}{{semiverbatim}}
  The text inside this environment is typeset like verbatim
  text. However, the characters |\|, |{|, and |}| retain their
  meaning. Thus, you can say things like
\begin{verbatim}
\alert<1->{std::cout << "AT&T likes 100% performance";}
\end{verbatim}
  To typeset the three characters |\|, |{|, and |}| you can use the
  commands |\\| (which is redefined inside this environment---you do
  not need it anyway), |\{|, and |\}|. Thus in order to get typeset
  ``|\alert<1>{X}|'' you can write |\\alert<1>\{X\}|.
\end{environment}


\subsection{Abstract}

The |abstract| environment is overlay-specificiation-aware in \beamer:


\begin{environment}{{abstract}\sarg{action specification}}
  You can use this environment to typeset an abstract.

  \begin{element}{abstract}\no\yes\yes
    These \beamer-color and -font are used to typeset the abstract. If
    a background color is set, this background color is used as
    background for the whole abstract by default.
  \end{element}

  \begin{element}{abstract title}\yes\yes\yes
    \colorparents{titlelike}
    This template is used for the title. By default, this inserts
    the word |\abstractname|, centered. The background color is ignored.
  \end{element}

  \begin{element}{abstract begin}\yes\no\no
    This template is inserted at the very beginning of the abstract,
    before the abstract title and the \meta{environment
    contents} is inserted.
  \end{element}

  \begin{element}{abstract end}\yes\no\no
    This template is inserted at the end of the abstract, after the
    \meta{environment contents}.
  \end{element}
\end{environment}




\subsection{Verse, Quotations, Quotes}

\LaTeX\ defines three environments for typesetting quotations and
verses: |verse|, |quotation|, and |quote|. These environments are also
available in the \beamer\ class, where they are
overlay-specification-aware. If an overlay specification is given, the
verse or quotation is shown only on the specified slides and is
covered otherwise. The difference between a |quotation| and a |quote|
is that the first has paragraph indentation, whereas the second does
not. 

You can change the font and color used for these by changing the
\beamer-colors and -fonts listed below. Unlike the standard \LaTeX\
environments, the default font theme typesets a verse in an italic
serif font, quotations and quotes are typeset using an italic font
(whether serif or sans-serif depends on the standard document font).


\begin{environment}{{verse}\sarg{action specification}}
  You can use this environment to typeset a verse.

  \begin{element}{verse}\no\yes\yes
    These \beamer-color and -font are used to typeset the verse. If
    a background color is set, this background color is used as
    background for the whole abstract. The default font is italic
    serif. 
  \end{element}

  \begin{element}{verse begin}\yes\no\no
    This template is inserted at the beginning of the verse.
  \end{element}

  \begin{element}{verse end}\yes\no\no
    This template is inserted at the end of the verse.
  \end{element}
\end{environment}


\begin{environment}{{quotation}\sarg{action specification}}
  Use this environment to typeset multi-paragraph quotations. Think
  again, before presenting multi-paragraph quotations.

  \begin{element}{quotation}\no\yes\yes
    These \beamer-color and -font are used to typeset the quotation.
  \end{element}

  \begin{element}{quotation begin}\yes\no\no
    This template is inserted at the beginning of the quotation.
  \end{element}

  \begin{element}{quotation end}\yes\no\no
    This template is inserted at the end of the quotation.
  \end{element}
\end{environment}


\begin{environment}{{quote}\sarg{action specification}}
  Use this environment to typeset a single-paragraph quotation.

  \begin{element}{quote}\no\yes\yes
    These \beamer-color and -font are used to typeset the quote.
  \end{element}

  \begin{element}{quote begin}\yes\no\no
    This template is inserted at the beginning of the quote.
  \end{element}

  \begin{element}{quote end}\yes\no\no
    This template is inserted at the end of the quote.
  \end{element}
\end{environment}


\subsection{Footnotes}

First a word of warning: Using footnotes is usually not a good
idea. They disrupt the flow of reading.

You can use the usual |\footnote| command. It has been augmented to
take an additional option, for placing footnotes at the frame
bottom instead of at the bottom of the current minipage.

\begin{command}{\footnote\sarg{overlay
      specification}\oarg{options}\marg{text}} 
  Inserts a footnote into the current frame. Footnotes will always be
  shown at the bottom of the current frame; they will never be
  ``moved'' to other frames. As usual, one can give a number as
  \meta{options}, which will cause the footnote to use that
  number. The \beamer\ class adds one additional option:
  \begin{itemize}
  \item \declare{|frame|} causes the footnote to be shown at the
    bottom of the frame. This is normally the default behavior anyway,
    but in minipages and certain blocks it makes a difference. In a
    minipage, the footnote is usually shown as part of the minipage
    rather than as part of the frame.
  \end{itemize}

  If an \meta{overlay specification} is given, this causes the
  footnote \meta{text} to be shown only on the specified slides. The
  footnote symbol in the text is shown on all slides.

  \example |\footnote{On a fast machine.}|
  \example |\footnote[frame,2]{Not proved.}|
  \example |\footnote<.->{Der Spiegel, 4/04, S.\ 90.}|

  \begin{element}{footnote}\yes\yes\yes
    This template will be used to render the footnote. Inside this
    template, the following two inserts can be used:
    \begin{itemize}
    \iteminsert{\insertfootnotetext}
      Inserts the current footnote text.
    \iteminsert{\insertfootnotemark}
      Inserts the current footnote mark (like a raised number). This mark
      is computed automatically.
    \end{itemize}
  \end{element}

  \begin{element}{footnote mark}\no\yes\yes
    This \beamer-color/-font is used when rendering the footnote mark,
    both in the text and at the beginning of the footnote itself.
  \end{element}
\end{command}


%%% Local Variables: 
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