[Tex/LaTex] ntheorem and attributions without redefinining a theorem style

ntheoremtheorems

I'm using the theoremstyle marginbreak from the package ntheorem as follows:

\theoremstyle{marginbreak}
\theoremindent1cm
\newtheorem{teo}{Theorem}[chapter]

The problem is that when I want to specify a reference or an attribution as in

\begin{teo}[Pitagora]
    $a^2+b^2=c^2$
\end{teo}

the text between square brackets is showed in a bold font.

I've seen this answer: ntheorem and theoremname. But since I'm not comfortable with theoremstyles I'm not able to redefine the marginbreak style.

On the other hand the following works:

\begin{teo}[\normalfont Pitagora]
    $a^2+b^2=c^2$
\end{teo}

but of course writing everytime \normalfont is not a solution. If this was a command, instead of an envirovment, I would do something like this:

\renewcommand{\teo}[1]{\teo{\normalfont #1}}

But with environments I don't know how to do it.

Any suggestions?

Best Answer

The answer to your question involves performing a \renewtheoremstyle on the marginbreak environment. In the MWE below, note that (##3) has been expanded to {\normalfont(##3)}. With this change, only the optional title of the theorem header and the surrounding parentheses are set in the normal (non-bold) font.

Relative to your example code, I've also changed the amount of \theoremindent to 0cm to make the default positioning of the theorem header visible; use a positive (negative) length to right-shift (left-shift) the position of the theorem header.

\documentclass{book}
\usepackage{ntheorem,lipsum}
\makeatletter
\renewtheoremstyle{marginbreak}%
  {\item[\rlap{\vbox{\hbox{\theorem@headerfont
    \llap{##2}\hskip\labelsep\relax ##1\theorem@separator}\hbox{\strut}}}]}
  {\item[\rlap{\vbox{\hbox{\theorem@headerfont
    \llap{##2}\hskip\labelsep\relax ##1        {\normalfont(##3)}\theorem@separator}\hbox{\strut}}}]}
\makeatother

\theoremstyle{marginbreak}
\setlength\theoremindent{0cm} % default
\newtheorem{teo}{Theorem}[chapter]

\begin{document}
\chapter{Start}
\begin{teo}[Pitagora]
$a^2+b^2=c^2$
\end{teo}
\lipsum[2] % filler text
\end{document}

enter image description here

Related Solutions

[Tex/LaTex] Overfull \hbox produced by ntheorem subtitles

No; it's not a bug, although it could be considered a bad design choice; ntheorem uses the optional argument of \item to typeset the theorem header (name, number and annotation), and that causes the problem (I guess that the package author thought that an annotation shouldn't be too long). You can define your own style, imitating the existing plain style but modifying the undesired behaviour, so that you can now have annotations spanning several lines; the definition would be something along these lines, I used a checkmark (\Checkmark from bbding) as the endmark:

\documentclass[12pt]{article}
\usepackage{bbding}
\usepackage{amsmath}
\usepackage[thmmarks,amsmath,amsthm,thref]{ntheorem}

\makeatletter
\newtheoremstyle{Myplain}%
  {\item[\hskip\labelsep \theorem@headerfont ##1\ ##2\theorem@separator]}%
  {\item[\hskip\labelsep \theorem@headerfont ##1\ ##2]\theorem@headerfont (##3)\theorem@separator\newline\normalfont\itshape}
\newtheoremstyle{nonumberMyplain}%
  {\item[\theorem@headerfont\hskip\labelsep ##1\theorem@separator]}%
  {\item[\theorem@headerfont\hskip \labelsep ##1]\theorem@headerfont (##3)\theorem@separator\newline\normalfont\itshape}
\makeatother

\theoremstyle{Myplain}
\theoremsymbol{\Checkmark}
\newtheorem{example}{Example}

\begin{document}
\begin{example}[blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah]
Content
\end{example}

\end{document}

Another option would be to use the thmtools package which doesn't use \item to build its theorem-like structures, thus providing an easier solution (the same checkmark was used in this example):

\documentclass[12pt]{article}
\usepackage{amsthm}
\usepackage{thmtools}
\usepackage{bbding}
\declaretheoremstyle[
  spaceabove=6pt, spacebelow=6pt,
  headfont=\normalfont\bfseries,
  notefont=\mdseries\bfseries,
  qed=\Checkmark,
  notebraces={(}{)},
  bodyfont=\itshape,
]{mystyle}
\declaretheorem[style=mystyle]{Example}


\begin{document}
\begin{Example}[blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah]
Content
\end{Example}

\end{document}

[Tex/LaTex] ntheorem with the [amsthm] option ignores styling of a theorem environment

It is possible to "lift" the proof environment code from ntheorem:

\documentclass{article}
\usepackage[thmmarks]{ntheorem}% http://ctan.org/pkg/ntheorem

\makeatletter
\newcommand{\openbox}{\leavevmode
  \hbox to.77778em{%
  \hfil\vrule
  \vbox to.675em{\hrule width.6em\vfil\hrule}%
  \vrule\hfil}}
\gdef\proofSymbol{\openbox}
\newcommand{\proofname}{Proof.}
\newcounter{proof}\newcounter{currproofctr}\newcounter{endproofctr}%
\newenvironment{proof}[1][\proofname]{
  \th@nonumberplain
  \def\theorem@headerfont{\itshape}%
  \normalfont
  %\theoremsymbol{\ensuremath{_\blacksquare}}
  \@thm{proof}{proof}{#1}}%
  {\@endtheorem}
\makeatother

\theoremstyle{plain}
\theoremheaderfont{\normalfont\itshape}
\theorembodyfont{\normalfont}
\newtheorem*{myenv}{Note}

\begin{document}
\begin{myenv}
The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog.
\begin{proof}
This statement is true, because the fox did jump over the lazy dog.
\end{proof}
\end{myenv}
\end{document}

ntheorem with amsthm proof environment

The QED-symbol is displayed when using the thmmarks package option of ntheorem. In ntheorem this is manually defined in \openbox, and subsequently used as \proofSymbol.

Best Answer

Related Solutions

[Tex/LaTex] Overfull \hbox produced by ntheorem subtitles

[Tex/LaTex] ntheorem with the [amsthm] option ignores styling of a theorem environment

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