Generate math symbols from argument

Question

I have been trying to create a small latex math symbol reference. My list will require repetition of lines like \textbackslash lfloor - $\lfloor$. I want to create a command that takes in one argument that is either the symbol name lfloor or the command itself \lfloor. But in either scenario, I have trouble showing the other case. How can I define such command?

Answer 1

If it is only about single control sequence tokens and if eTeX-extensions are available, you can probably use a combination of \string, \scantokens and the \verb-command:

\documentclass{article}

\newcommand\myCsPrintCommand[1]{%
  \expandafter\InnermyCsPrintCommand\expandafter{\string#1}%
}%
\begingroup
\makeatletter
\catcode`\?=14\relax
\catcode`\%=12\relax
\@firstofone{?
  \endgroup
  \newcommand\InnermyCsPrintCommand[1]{?
    \scantokens\expandafter{\string\verb|#1| -- $#1$%}?
  }?
}%
% The trickery above is needed for bringing a %-char/comment-char
% into \scantokens' argument. That in turn is needed for neutralizing
% the endline-character inserted at the end of \scantokens' argument.

\begin{document}
\myCsPrintCommand{\lfloor} 
\myCsPrintCommand{\rfloor}
\end{document} 

In my opinion this is sort of overkill, but I nonetheless decided to show the underlying \scantokens-trickery as it can be used not only with \verb but with other commands also whose arguments usually should not be delivered via macros but via reading and tokenizing input as these arguments should be read/tokenized under different catcode-régime, e.g. \lstinline from the listings-package, or whatever else is to be used for pretty-printing the control words.

Nonetheless the following example is my attempt at providing a generic macro \myCsPrintCommand which lets you format the pretty-printing of a control sequence with commands like \verb or \lstinline as well:

\documentclass{article}
\usepackage{color, listings}

%%----------------------------------------------------------------------
%% Both pretty-print a control sequence and typeset the result 
%% from carrying out the control sequence:
%%----------------------------------------------------------------------
%% \myCsPrintCommand{<stringified-printing-command>}%
%%                  {<verb-delimiter>}%
%%                  {<separator>}%
%%                  {<formatting-when-carrying-out-command>}%
%%                  {<control sequence to typeset>}%
%%
%% ->
%% either
%%   <stringified-printing-command><verb-delimiter><control sequence to typeset><verb-delimiter>%
%%   <separator><formatting-when-carrying-out-command>{<control sequence to typeset>}
%% or
%%   <stringified-printing-command>{<control sequence to typeset>}%
%%   <separator><formatting-when-carrying-out-command>{<control sequence to typeset>}
%%
%% <stringified-printing-command> prints the character-sequence that
%% forms the control sequence.
%% <stringified-printing-command> either can be something with \verb-syntax -
%% in this case you need to specify a <verb-delimiter>, e.g., |, or
%% can be something that does process one undelimited argument -
%% in this case you need to leave the <verb-delimiter>-argument empty.
%% 
%% <formatting-when-carrying-out-command> influences how the result from
%% carrying out <control sequence to typeset> gets typeset.
%% <formatting-when-carrying-out-command> can be a control sequence that
%% processes one undelimited argument.
%%
%% e.g., \myCsPrintCommand{\verb}{|}{--}{\textbf}{\LaTeX}
%%       -> \verb|\LaTeX|--\textbf{\LaTeX}
%% e.g., \myCsPrintCommand{\verb}{|}{ -- }{\ensuremath}{\lfloor}
%%       -> \verb|\lfloor| -- \ensuremath{\lfloor}
%% e.g., \myCsPrintCommand{\myownstringifier}{}{--}{\ensuremath}{\lfloor}
%%       -> \myownstringifier{\lfloor}--\ensuremath{\lfloor}
%% 
\newcommand\myCsPrintCommand[5]{%
  \expandafter\InnermyCsPrintCommand\expandafter{\string#5}{#1}{#2}{#3}{#4}%
}%
\begingroup
\makeatletter
\catcode`\?=14\relax
\catcode`\%=12\relax
\@firstofone{?
  \endgroup
  ??----------------------------------------------------------------------
  ?? Expandably within two expansion steps check whether argument is empty:
  ??----------------------------------------------------------------------
  ?? \UDCheckWhetherNull{<Argument which is to be checked>}%
  ??                     {<Tokens to be delivered in case that argument
  ??                       which is to be checked is empty>}%
  ??                     {<Tokens to be delivered in case that argument
  ??                       which is to be checked is not empty>}%
  ??
  ?? The gist of this macro comes from Robert R. Schneck's \ifempty-macro:
  ?? <https://groups.google.com/forum/#!original/comp.text.tex/kuOEIQIrElc/lUg37FmhA74J>
  ??......................................................................
  \newcommand\UDCheckWhetherNull[1]{?
    \romannumeral0\expandafter\@secondoftwo\string{\expandafter
    \@secondoftwo\expandafter{\expandafter{\string#1}\expandafter
    \@secondoftwo\string}\expandafter\@firstoftwo\expandafter{\expandafter
    \@secondoftwo\string}\expandafter\expandafter\@firstoftwo{ }{}?
    \@secondoftwo}{\expandafter\expandafter\@firstoftwo{ }{}\@firstoftwo}?
  }?
  \newcommand\InnermyCsPrintCommand[5]{?
    \UDCheckWhetherNull{#3}{?
      \scantokens\expandafter{\string#2{#1}#4#5{#1}%}?
    }{?
     \scantokens\expandafter{\string#2#3#1#3#4#5{#1}%}?
    }?
  }?
}%
% The trickery above is needed for bringing a %-char/comment-char
% into \scantokens' argument. That in turn is needed for neutralizing
% the endline-character inserted at the end of \scantokens' argument.

\begin{document}

%% \myCsPrintCommand{<stringified-printing-command>}%
%%                  {<verb-delimiter>}%
%%                  {<separator>}%
%%                  {<formatting-when-carrying-out-command>}%
%%                  {<control sequence to typeset>}%

Example with \verb|\verb|:

\myCsPrintCommand{\verb}{|}{ -- }{\ensuremath}{\lfloor} 

\myCsPrintCommand{\verb}{|}{ -- }{\ensuremath}{\rfloor}

Example with \verb|\lstinline|:

\myCsPrintCommand{\lstinline[language={[LaTeX]TeX}]}{|}{ -- }{\ensuremath}{\lfloor} 

\myCsPrintCommand{\lstinline[language={[LaTeX]TeX}]}{|}{ -- }{\ensuremath}{\rfloor}

Example with \verb|\mybluestringified|:

\newcommand\mybluestringified[1]{%
  \textcolor{blue}{\texttt{\string#1}}%
}%

\myCsPrintCommand{\mybluestringified}{}{ -- }{\ensuremath}{\lfloor} 

\myCsPrintCommand{\mybluestringified}{}{ -- }{\ensuremath}{\rfloor}

% You can put the call to \myCsPrintCommand into a macro:

\newcommand\printitwithverb{%
  \myCsPrintCommand{\verb}{|}{ -- }{\ensuremath}%
}%
\newcommand\printitwithlstinline{%
  \myCsPrintCommand{\lstinline[language={[LaTeX]TeX}]}{|}{ -- }{\ensuremath}%
}%
\newcommand\printitwithmybluestringified{%
  \myCsPrintCommand{\mybluestringified}{}{ -- }{\ensuremath}%
}%

Example with \verb|\printitwithverb|:

\printitwithverb{\lfloor} 

\printitwithverb{\rfloor}

Example with \verb|\printitwithlstinline|:

\printitwithlstinline{\lfloor} 

\printitwithlstinline{\rfloor}

Example with \verb|\printitwithmybluestringified|:

\printitwithmybluestringified{\lfloor} 

\printitwithmybluestringified{\rfloor}

\end{document}