Removing a backslash "\" when passing arguments to newcommand

Question

Consider the following minimal example:

\documentclass{article}

\usepackage{glossaries}
\makeglossaries

\newcommand{\NewS}[4]{
    % Q1: How can I use argument #1 without the backslash in the following line?
    \newglossaryentry{symb:#4}{
        name=\ensuremath{#2},
        description={\nopostdesc #3}, 
        sort=sym#4,
    }

    % Q2: Why is the space between the '}' necessary?
    \def#1{\ensuremath{#2} } 
}

\NewS{\power}{P}{the power of something}{power}

\begin{document}
    One can refer to the symbol via \power and \gls{symb:power} and. 
\end{document}

The two questions I have are already inserted in the example. In particular I am searching for a way to remove the backlash of the string \power which I pass as a first argument to the newcommand so that I can write something like:

\newglossaryentry{symb:WITHOUT_BACKSLASH(#1)}{

And secondly I don't understand why I have to leave a space between the two braces in the \def in order to get "P and" in the output and not "Pand" - which is what I get when I remove the space. If I directly write \ensuremath{P} and I don't see any problems so I am just curious.

Thanks for your help!

Regards

Related Question: How to extract the name of a macro?. – Peter Grill Mar 05 '15 at 21:42 — Peter Grill, Mar 05 '15 at 21:42

egreg · Accepted Answer · 2011-06-11T12:50:27.037

8

It depends on how you need to use the control sequence name. A method for printing the control sequence name without the backslash is

\begingroup\escapechar=-1\edef\x{\endgroup\string\power}\x

In a definition, the explicit \power will be #1. But, again, it depends on what you want to do with the string.

The second question is a very frequently asked one: TeX ignores spaces after control sequence names like \power. Don't put a space in the definition, but rather write \power{} in the document.

If you just want to spare an argument, then use the LaTeX kernel function

\makeatletter
\newcommand{\NewS}[3]{%
    \newglossaryentry{symb:#1}{
        name=\ensuremath{#2},
        description={\nopostdesc #3}, 
        sort=sym#1,
    }%
    \@namedef{#1}{\ensuremath{#2}}%
}
\makeatother

Now \NewS{power}{P}{the power of something} will suffice and you will be able to say

\begin{document}
One can refer to the symbol via \power{} and \gls{symb:power} and. 
\end{document}

edited Jun 11 '11 at 12:50

answered Jun 11 '11 at 10:41

egreg

1,121,712

Regarding the second question: I thought that \power is treated like a string when I use it as an argument of a command, e.g. in \NewS{\power}{...} above and that I can access this string via #1 in the definition of the command \NewS. Thus I understand \def#1{something} as \def\power{something}. I was therefore looking for a way to use the string without the backslash in the line \newglossaryentry{symb:<insert string 'power' here>}{. But I think that Ians answer is the better way to go. – TriSSSe Jun 11 '11 at 12:01
To avoid the {} everytime you use \power, you could include the {xspace} package, add \xspace to the end of the defintition of \power, and then use it as The \power is the \power. and should have a space before the is but not before the period. – Peter Grill Jun 11 '11 at 17:26
Another option (which is slightly shorter and I think better because it doesn't look like it is passing an empty argument to a macro) is to use \—that is, a backslash followed by a space (or new line)— after \power: ...via \power\ and .... – TH. Jun 12 '11 at 10:19

Leo Liu · Answer 2 · 2011-06-11T15:49:37.907

In expl3, there is a \cs_to_str:N function to get the macro name without a backslash. If you are not familar with expl3 syntax, you can define a clone of the function:

\documentclass{minimal}
\usepackage{expl3}
\ExplSyntaxOn
  \let\cstostr\cs_to_str:N
\ExplSyntaxOff
\begin{document}
\cstostr\foobar
% We obtain: foobar
\end{document}

Note: \cs_to_str:N is fully expandable. Thus it's robust enough.

It's nontrivial to define a command like \cs_to_str:N. You can check the definition in source3 document, if you want to pry.

Here is my version of \cstostr:

\makeatletter
\def\cstostr#1{%
  \expandafter\@gobble\detokenize\expandafter{\string#1}}
\makeatother

The definition is much simpler than LaTeX3's \cs_to_str:N, but may fail when \escapechar is unusual. It is also fully expandable.

TeX ignores all spaces after a all-letter macro by default. To solve the question about space, you can use:

\power\ and

or

\power{} and

score 5 · Answer 3 · answered Jun 11 '11 at 10:50

5

An alternative approach is to create the macro from the string.

\documentclass{minimal}
\newcommand\makemacro[1]{\expandafter\def\csname#1\endcsname{arnold}}
\begin{document}
\makemacro{power}
\power
\end{document}

answered Jun 11 '11 at 10:50

Ian Thompson

43,767

1

Thanks, this works. And it seems to be the more natural approach. – TriSSSe Jun 11 '11 at 11:45

Removing a backslash "\" when passing arguments to newcommand

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