[Tex/LaTex] How to create two commands with the same name but different number of parameters

macros

I want to define a command with the same name, but a different number of parameters.

I'm considering something like this:

\documentclass{article}

\usepackage{hyperref}

\newcommand{\quelle}[1]{\textit{(Quelle: \url{#1})})}
\newcommand{\quelle}[2]{\textit{(Quelle: \url{#1} Absatz: #2)})}

\begin{document}

    Test: \quelle{www.wikipedia.de}
    Test: \quelle{www.wikipedia.de, sometext}


\end{document}

If I try to compile this, I get the following result:

Command \quelle already defined. ...2]{\textit{(Quelle: \url{#1} Absatz: #2)})}

Thank you for your help!

Best Answer

The only change from the requested syntax is to use a ! as the separator between the http reference and "sometext", as I figured a comma , was much more likely to appear as part of "sometext:.

\documentclass{article}
\usepackage{hyperref,listofitems}
\newcommand{\quelle}[1]{%
  \setsepchar{!}%
  \readlist\qarg{#1}%
  (\textit{Quelle: \url{\qarg[1]}}%
  \ifnum\listlen\qarg[]>1\relax\textit{ Absatz: \qarg[2]}\fi%
  )%
}
\begin{document}
    Test: \quelle{www.wikipedia.de}
    Test: \quelle{www.wikipedia.de! sometext}
\end{document}

Related Solutions

[Tex/LaTex] Use column-separator & (ampersand) inside \newenvironment

The problem is that the \begin{...} and \end{...} pair commands automatically create a "group" so that, in effect, the & and \\ are "out of scope" for the tabular, while inside the "production" environment they just show up at a place where the compiler is not expecting them.

A second problem with your definitions is that, even if they would work, they would be adding an extra \\ at the end of the tabular, adding an unwanted space at the end. Perhaps some more appropriate definitions would be

\documentclass[a4paper,10pt]{article}

\newcommand{\production}[1]{#1 ::= &}
\newenvironment{grammar}{\tabular{p{3cm}l}}{\endtabular}

\begin{document}
\begin{grammar}
\production{XmlStartTag} ... \\
\production{XmlOtherTag} ... \\
\production{XmlEndTag} ...
\end{grammar}
\end{document}

Note no \\ at the end of the last production. Also in the definition of the grammar you don't need to repeat the work of \begin/\end, and you can instead directly use \tabular and \endtabular.

[Tex/LaTex] What’s wrong with the newcommand

The first problem you have is that you cannot create a macro starting with \end... when using \newcommand. This check is defined inside the LaTeX kernel as part of an \@ifdefinable condition. To circumvent this you need to use TeX directives. That is,

\def\endexer#1{<stuff>}

rather than

\newcommand{\endexer}[1]{<stuff>}

Secondly, the \newcommand syntax has the following structure (see source2e.pdf):

\newcommand*{\foo}[<i>][<j>]{<text>}

* is optional
\foo is the command to be created
<i> is the number of arguments to gobble (up to 9); this references mandatory or a possible optional argument
<j> is the default value of the first optional argument (if it exists does not exist); can only have one
<text> is the macro definition when using \foo

For \newcommand{\foo}[1]{stuff #1} you would use it as \foo{<stuff>}, not \foo[<stuff>]. This latter usage would have required a definition of \foo of the form

\newcommand{\foo}[1][]{<stuff>}

Note the second set of [], denoting that \foo takes an optional argument (that is empty by default/if not specified).

Specific to your case, use \endexer{123}, not \endexer[123].

Here is a minimal example:

enter image description here

\documentclass{article}
\usepackage{hyperref}
\newcommand{\qqq}{\section{Question}\begin{enumerate}}
\newcommand{\exer}{\end{enumerate}\section{Exercises}\begin{enumerate}}
\def\endexer#1{\end{enumerate}\href{my.url.com/path/{#1}}{Take the quiz}}
\begin{document}

\qqq
\item What is $2+3$?
\exer
\item Write a program to compute $2+3$.
\endexer{123}

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] Use column-separator & (ampersand) inside \newenvironment

[Tex/LaTex] What’s wrong with the newcommand

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