Environment with argument and optional argument

Question

I want to create an environment that receives an argument and an optional argument in such a way that the first argument will be a title and the optional argument will decide whether the title should be justified to the left or centered. It's possible without any package?

Yes, this is possible and there are many packages, that provide such environments already, e.g. mdframed or tcolorbox, with lot of additional features. — , Feb 01 '19 at 17:25

score 5 · Answer 1 · 2019-02-01T18:25:06.403

5

Without any package: Using an optional argument that is checked with \pdfstrcmp (a pdftex primitive).

If #1 is equal to left, the title is left aligned, in any other case it is centered.

\documentclass{article}

\newenvironment{foo}[2][]{%
  \ifnum\pdfstrcmp{#1}{left}=0%
  #2%
  \else
  \hfil#2\hfil%
  \fi%
  \medskip

}{}

\newcommand{\footitleformat}[1]{%
  \bfseries\MakeUppercase{#1}%
}

\newenvironment{fooother}[2][]{%
  \ifnum\pdfstrcmp{#1}{left}=0%
  \footitleformat{#2}%
  \else
  \begingroup
  \centering 
  \footitleformat{#2}%

  \endgroup
  \fi%
  \medskip

}{}



\begin{document}

\begin{foo}{This is centered}
  Foo stuff
\end{foo}


\begin{foo}[left]{This is not centered}
Other Foo stuff
\end{foo}

\begin{fooother}{This is centered again}

Yet another Foo stuff
\end{fooother}


\end{document}

\documentclass{article}

\newenvironment{foo}[2][]{%
  \ifnum\pdfstrcmp{#1}{left}=0%
  #2%
  \else
  \hfil#2\hfil%
  \fi%
  \medskip

}{}


\begin{document}

\begin{foo}{This is centered}
  Foo stuff
\end{foo}


\begin{foo}[left]{This is not centered}
Other  Foo stuff
\end{foo}


\end{document}

edited Feb 01 '19 at 18:25

answered Feb 01 '19 at 17:34

I try to use {\centering\bfseries\MakeUppercase{#2}} but the text is not center... – Joan Feb 01 '19 at 18:01
@Joan: You need an empty line after \centering – Feb 01 '19 at 18:04
Don't understand. – Joan Feb 01 '19 at 18:13
@Joan: I changed the answer: I was too short in my explanation ... you need an empty line after the text that is to be centered. – Feb 01 '19 at 18:25
I have add \begingroup \endgroup to definition of \footitleformat. Thanks @Christian Hupfer – Joan Feb 01 '19 at 19:12
I have a problem... I have add the code to myclass.cls file, but don't work. Only work if I add the code a .tex file. – Joan Feb 01 '19 at 19:44
@Joan: I cannot solve that problem because I have no idea what your myclass.cls does. And it's another question. – Feb 01 '19 at 19:50
My class is based on book.cls. I just added your code to this file, but don't work. – Joan Feb 01 '19 at 19:54
@Joan: Again: I can't help you: My code does nothing special -- it uses standard TeX/LaTeX macros from the LaTeX core! There is nothing that should interfere with book.cls etc. You must be doing something wrong in your class. Writing a class requires some deeper knowledge of LaTeX etc. – Feb 01 '19 at 19:56
I'm sorry, it was my fault, I accidentally "deleted" the empty line...I would like to know why this empty line is necessary. – Joan Feb 01 '19 at 20:16
1

@Joan: See the answers to the question here -- it takes too long to explain this in a comment – Feb 01 '19 at 20:25

score 5 · Accepted Answer · answered Feb 01 '19 at 21:53

5

The optional argument can be l or c (default c).

\documentclass{article}

\makeatletter
\newenvironment{something}[2][c]
 {\begin{\csname #1@somethingtitle\endcsname}
  \bfseries #2
  \end{\csname #1@somethingtitle\endcsname}}
 {\par\addvspace{\topsep}}
\newcommand\l@somethingtitle{flushleft}
\newcommand\c@somethingtitle{center}
\makeatother

\begin{document}

\begin{something}{This is centered}
This is the environment's contents
This is the environment's contents
This is the environment's contents
This is the environment's contents
\end{something}

\begin{something}[l]{This is left flush}
This is the environment's contents
This is the environment's contents
This is the environment's contents
This is the environment's contents
\end{something}

\end{document}

answered Feb 01 '19 at 21:53

egreg

1,121,712

I would like to know why you use the char @? – Joan Feb 01 '19 at 22:10
@Joan In order to avoid clashes with user macros. – egreg Feb 01 '19 at 23:02
in the case that I want to add an optional argument that allows to decide if the title wants to be added to the ToC, how could I do it? – Joan Feb 21 '19 at 21:04

score 3 · Answer 3 · answered Feb 01 '19 at 20:34

Write the environment to take a key-valued optional argument

\documentclass{article}

\usepackage{xkeyval}

\makeatletter
% From the xkeyval documentation (section 3.3 Choice keys)
% http://texdoc.net/texmf-dist/doc/latex/xkeyval/xkeyval.pdf
\define@choicekey*{paralign}{align}[\val\nr]{left,center,right}[center]{% Add align=? key-value
  \gdef\titlealign{}%
  \ifcase\nr\relax
    \gdef\titlealign{\raggedright}\or% 0 = left
    \gdef\titlealign{\centering}\or% 1 = center
    \gdef\titlealign{\raggedleft}% 2 = right
  \fi
}
\define@cmdkey{paralign}{format}[]{}% Add format=? key-value

\newenvironment{mytitle}[2][]{%
  \par\addvspace{\medskipamount}
  \begingroup
    \setkeys{paralign}{%
      align,format,% Default settings (align=center,format={})
      #1}% Local settings
    \titlealign \cmdKV@paralign@format #2%
    \par
  \endgroup
  \nobreak\smallskip
}{%
  \par\addvspace{\medskipamount}
}
\makeatother

\begin{document}

\begin{mytitle}{Centred titled}
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus placerat 
enim ligula, a efficitur augue sodales non\ldots
\end{mytitle}

\begin{mytitle}[align=left]{Left-aligned title}
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus placerat 
enim ligula, a efficitur augue sodales non\ldots
\end{mytitle}

\begin{mytitle}[align=right,format=\bfseries]{Right-aligned title}
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus placerat 
enim ligula, a efficitur augue sodales non\ldots
\end{mytitle}

\end{document}

Environment with argument and optional argument

3 Answers3

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