[Tex/LaTex] Print small TeX code verbatim and render it

macrosverbatim

To write some documentation, I would like the ability to define a command such as

\showcase{x^{y}\in\Omega}

which expands to something roughly equivalent to

\verb|x^{y}\in\Omega| & $x^{y}\in\Omega$ \\

so that I can show what the latex code looks like and how does it show on the document.

Now I now that it isn't really possible to use \verb for this because it's really fragile and you can't pass arguments from a macro to it. But, assuming that I'm not trying to write anything crazy in the argument to \showcase (e.g. braces are always balanced, I don't care much if spaces are collapsed, no %'s inside), is there a way to define such a command?

Update

\detokenize does (almost) exactly what I want. Take the following example

\newcommand\showcase[1]{{\ttfamily\detokenize{#1}} & $#1$}
\begin{tabular}{cc|cc}
\showcase{x^{y}}      & \showcase{\hat{x}, \bar{x}} \\
\showcase{x_{y}}      & \showcase{f\colon X \to Y} \\
\showcase{x'}         & \showcase{\sqrt{x+2}} \\
\showcase{x''_{2}}    & \showcase{2 < x \leq 4} \\
\showcase{A^{1}_{2}}  & \showcase{\frac{a+b}{c+d}} \\
\showcase{3\pi/4}     & \showcase{\int_{0}^{1} x^{2} \,dx} \\
\showcase{x\in\Omega} & \showcase{A \cup B \subseteq C \cap D}
\end{tabular}

Which produces the output:

enter image description here

My minor quibbles are that:

The double '' seems to have been collapsed into a "
I find mildly annoying the spaces after control sequences. I know why they are there, but could there be a way to remove the space if it is not followed by a letter or number? (Or, conversely, if followed by { or _)

Best Answer

For math mode this should work.

\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand{\showcase}{v}
 {
  \texttt{#1} & \tl_rescan:nn { } { $#1$ }
 }
\ExplSyntaxOff

\begin{document}
\begin{tabular}{cc|cc}
\showcase{x^{y}}      & \showcase{\hat{x}, \bar{x}} \\
\showcase{x_{y}}      & \showcase{f\colon X \to Y} \\
\showcase{x'}         & \showcase{\sqrt{x+2}} \\
\showcase{x''_{2}}    & \showcase{2 < x \leq 4} \\
\showcase{A^{1}_{2}}  & \showcase{\frac{a+b}{c+d}} \\
\showcase{3\pi/4}     & \showcase{\int_{0}^{1} x^{2} \,dx} \\
\showcase{x\in\Omega} & \showcase{A \cup B \subseteq C \cap D}
\end{tabular}
\end{document}

enter image description here

Should you want to swap the columns, so the result appears before the code, just change the definition of \showcase inverting the cells:

\NewDocumentCommand{\showcase}{v}
 {
  \tl_rescan:nn { } { $#1$ } &  \texttt{#1}
 }

enter image description here

Related Solutions

[Tex/LaTex] Wrapping code (listings, verbatim, or other method) inside a newcommand

We recently considered adding some support for verbatim arguments to xparse. Starting from roughly 15/08/2011 (on the svn, not yet on CTAN), you can define a command with any combination of optional, mandatory and verbatim arguments. Each command defined with xparse has an argument signature which indicates what kind of argument it expects (the most common are m for normal mandatory argument, o for optional, s, for an optional star). With the new argument type, for instance, \verb would have a signature {sv}: an optional star followed by a verbatim argument.

For your case, I think a good idea is to give the signature { O{} +v O{} +v } to \codeListing:

#1, optional argument = options given to the first listing (default empty);
#2, verbatim argument = contents of the first listing;
#3, optional argument = options given to the second listing (default empty);
#4, verbatim argument = contents of the second listing;

The + mean that the next argument is "long". For non-verbatim arguments, this means that they may contain more than one paragraph. For verbatim arguments, it currently means that they may contain line-breaks, contrarily to the normal \verb command.

[Apart from the use of xparse, I based the example on Mike Renfro's answer.]

\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand {\codeListing} { O{} +v O{} +v }
  {
    \begin{table}[h]\centering
      \begin{tabular}[width=\textwidth]{ll}
        \newlinechar=\endlinechar
        \exp_args:Nx \scantokens
          {
            \string\begin{lstlisting}[\unexpanded{#1}]
              #2
            \string\end{lstlisting}
            &
            \string\begin{lstlisting}[\unexpanded{#3}]
              #4
            \string\end{lstlisting}
          }
      \end{tabular}
    \end{table}
  }
\ExplSyntaxOff
\usepackage[a4paper,margin=2cm]{geometry}
\usepackage{listings}
\usepackage{xcolor}
\usepackage{lipsum}
\begin{document}
\lipsum[1]

\codeListing[language=C,backgroundcolor=\color{yellow!30}]$
#include <stdio.h>

int main(void)
{
  printf("Hello world\n");
  return 0;
}
$[language=C++,backgroundcolor=\color{red!20}]$
#include <iostream>

using namespace std;
int main()
{
  cout << "Hello World!" << endl;
  return 0;
}
$

\lipsum[2]

\end{document}

[Tex/LaTex] Manual highlight of TeX code in a verbatim environment

I would use a replacement by literate:

\documentclass{standalone}

\usepackage{xcolor}
\usepackage{listings}

\lstset{basicstyle=\ttfamily,columns=flexible,language=[LaTeX]TeX,%
        texcl,%set comments in an extra line
        mathescape=false,escapechar=|,
literate={<B>}{\textcolor{blue}{\string\texbf}}1
         {<E>}{\textcolor{blue}{\string\emph}}1
         {<$>}{\textcolor{red}{\$}\color{green!60!black}}1
         {<$$>}{\textcolor{red}{\$}\normalcolor}1
         ,%
         texcsstyle=*\color{blue!70}\bfseries,
         texcs={end,begin,documentclass}
}
\begin{document}
\Huge
\begin{lstlisting}
\documentclass{article}

\begin{document}
Good morning <B>{sunshine}, the Earth says <E>{hello}! % it's from a song
See <$>a^2=b^2+c^2<$$> and tell me if you understand it. 
I don't want colors here, \emph{they are bad}. %true story
I can even understand $\pi$. % I prefer pie
\end{document}
\end{lstlisting}
\end{document}

enter image description here

Update

Best Answer

Related Solutions

[Tex/LaTex] Wrapping code (listings, verbatim, or other method) inside a newcommand

[Tex/LaTex] Manual highlight of TeX code in a verbatim environment

Related Question