[Tex/LaTex] Reindexing Theorem Numbers

amsthmnumberingtheorems

The amsthm package comes with an several theorem-like environments. Is there a way to adjust the indexing on a sequence of theorems to skip a number? That is, I would like to have it do something like this,

Theorem 1.

Theorem 3.

Theorem 4.

without having anything appearing in between Theorem 1 and Theorem 3.

Best Answer

\stepcounter{theorem} after Theorem 1.

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[Tex/LaTex] How to number floats in sequence with theorems

You can do this in a straightforward manner with amsthm; its \newtheorem command has the following syntax: \newtheorem{environment-name}[matched-counter]{text}[parent-counter]. Whatever counter is specified for matched-counter is used to number the created theorem; if none is given, a new counter is created. Thus, leveraging the existing figure counter, the following works:

\documentclass{amsart}
\usepackage{amsthm}

\newtheorem{theorem}[figure]{Theorem}
\newtheorem{definition}[figure]{Definition}

\begin{document}
  \begin{theorem}
    This is a theorem.
  \end{theorem}

  \begin{figure}
    \caption{This is a figure.}
  \end{figure}

  \begin{definition}
    This is a definition.
  \end{definition}
\end{document}

This will produce output along the lines of:

Figure 2. This is a figure.
Theorem 1. This is a theorem.
Definition 3. This is a definition.

So there is one obvious property of this which you might or might not like: figures are numbered as they are introduced in code, not as they appear. This is the standard behavior for figures, and would be less egregious if I actually had some text in my sample document, so I think it's relatively sensible. If you dislike it (as you allude to in your question), I'm not sure what to suggest. You could use the float placement [h], which tries to put the float exactly where it's specified in the source; however, TeX will still float it if it needs to. The float package provides an [H] float placement which unconditionally forces the (no-longer-floating) "float" to appear right there. Personally, I'd probably just let TeX number the floats as it wants to; from the text, the order of reference will probably be clear.

[Tex/LaTex] Theorem numbers in bold

You can redefine the internal command \swappedhead of amsart.cls which changes the number font when the \swapnumbers command is invoked. This can be done adding the lines between \makeatletter and \makeatother in my example code:

\documentclass{amsart}
\usepackage{amsthm}
\swapnumbers

\makeatletter
\def\swappedhead#1#2#3{%
  % original definition:
  % \thmnumber{\@upn{\the\thm@headfont#2\@ifnotempty{#1}{.~}}}%
  % change:
  \thmnumber{\@upn{\the\thm@headfont#2\@ifnotempty{#1}{.~}}}%
  \thmname{#1}%
  \thmnote{ {\the\thm@notefont(#3)}}}
\makeatother

\newtheoremstyle{dotless-thm}
  {3pt}
  {3pt}
  {\itshape}
  {}
  {\bfseries}
  {}
  {.5em}
  {}
\theoremstyle{dotless-thm}
\newtheorem{theo}{Theorem}

\begin{document}

\begin{theo}
Test
\end{theo}
\end{document}

EDIT: as Seamus has suggested in his answer, the fact that the number font for theorem-like structures changes if the \swapnumbers switch is in use is a feature provided by the AMS document classes.

Best Answer

Related Solutions

[Tex/LaTex] How to number floats in sequence with theorems

[Tex/LaTex] Theorem numbers in bold

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