Btukfyl

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!

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{!}%

  readlistqarg{#1}%

  (textit{Quelle: url{qarg[1]}}%

  ifnumlistlenqarg>1relaxtextit{ Absatz: qarg[2]}fi%

  )%

}

begin{document}

    Test: quelle{www.wikipedia.de}

    Test: quelle{www.wikipedia.de! sometext}

end{document}

I suggest an optional argument at the end, for example, with xparse and NewDocumentCommand.

If the optional argument is not given, quelle works like the intended one-argument version, if it is given Absatz #2 is printed in addition.

The check, whether it has been specified can be done with IfValueT{#2}{}.

documentclass{article}



usepackage{xparse}

usepackage{hyperref}



%newcommand{quelle}[1]{textit{(Quelle: url{#1})})}

NewDocumentCommand{quelle}{m+o}{textit{(Quelle: url{#1}IfValueT{#2}{Absatz: #2)}}}



begin{document}



    Test: quelle{www.wikipedia.de}



    Test: quelle{www.wikipedia.de}[sometext]





end{document}

I'd prefer a syntax with a leading optional argument, that's more in line with common LaTeX conventions.

Anyway, you can have your preferred syntax by defining a single quelle command: TeX cannot have two meanings for the same command.

documentclass{article}

usepackage{xparse}

usepackage{hyperref}



NewDocumentCommand{quelle}{ >{SplitArgument{1}{,}}m }{%

  makequelle#1%

}

NewDocumentCommand{makequelle}{mm}{%

  textit{%

    (Quelle: url{#1}%

    IfValueT{#2}{ Absatz: #2})%

  }%

}



begin{document}



Test: quelle{www.wikipedia.de}



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



end{document}

The argument is split at the first comma, if present, and passed as a pair of arguments to makequelle. If no comma is present, the second argument will make the test IfValueT false, so nothing will be printed.

The same output with a more common syntax:

documentclass{article}

usepackage{xparse}

usepackage{hyperref}



NewDocumentCommand{quelle}{om}{%

  textit{%

    (Quelle: url{#2}%

    IfValueT{#1}{ Absatz: #1})%

  }%

}



begin{document}



Test: quelle{www.wikipedia.de}



Test: quelle[sometext]{www.wikipedia.de}          



end{document}

The following code delivers what you're after using the following setup:

1. Use quelleattributes{<list>} to define the prefixes/attribute names in a comma-separate <list> you'll be supplying (Quelle, Absatz, ...).




2. Using etoolbox, we process the list sequentially, setting the attribute name, followed by the attribute. A text-comparison is done with each attribute name to see whether it matches Quelle. Only those are set using url, while the others are set as-is.

documentclass{article}



usepackage{etoolbox}

usepackage{hyperref}



newcounter{quellecnt}

makeatletter

newcommand{quelleattributes}[1]{%

  setcounter{quellecnt}{0}% Restart counter

  renewcommand*{do}[1]{% How to update each item

    stepcounter{quellecnt}% Step counter

    @namedef{quelle@thequellecnt}{##1}% Define quelle@<num> to attribute

  }%

  docsvlist{#1}% Process list

}



newcommand{quelle}[1]{%

  setcounter{quellecnt}{0}% Restart counter

  renewcommand*{do}[1]{%

    stepcounter{quellecnt}% Step counter

    letquelleformatrelax% Default formatting of attribute

    ifnumpdfstrcmp{@nameuse{quelle@thequellecnt}}{Quelle}=0

      defquelleformat{url}% Attribute should be a url

    fi

    @nameuse{quelle@thequellecnt}: quelleformat{##1} % Set attribute

  }

  (textit{%

    docsvlist{#1}unskip% Process list

  })%

}



makeatother



begin{document}



quelleattributes{%

  Quelle,

  Absatz%

}



Test: quelle{www.wikipedia.de}



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



end{document}