[Tex/LaTex] How to pass optional arguments to command

argumentsmacrosoptional arguments

I'm trying to write my own command that wraps the \VerbatimInput command. I'd like my command to take optional arguments (those given inside [...]) and pass those directly to \VerbatimInput[...]. Of course, if the optional arguments to my command are not given, then nothing should be passed to \VerbatimInput.

How can I do this? I'm a relative novice to creating custom commands in LaTeX.

Best Answer

If a macro argument is supposed to be a set of key-value pairs, making use of standard packages to the purpose (keyval, xkeyval and others), it is generally harmless to pass it the empty list.

\newcommand{\foo}[2][]{%
  <actions to be performed before>%
  \VerbatimInput[#1]{#2}%
  <actions to be performed after>%
}

is the method you're looking for, because fancyvrb does use keyval.

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[Tex/LaTex] \newcommand gives errors in math mode (with or without arguments)

Here is an alternative to your current situation - using an optional argument to specify the derivative order. This way you don't have to define a macro for "each" derivative:

\deriv[<order>]{<func>}{<var>}

Here's a minimal example:

enter image description here

\documentclass{article}
\newcommand{\deriv}[3][]{% \deriv[<order>]{<func>}{<var>}
  \ensuremath{\frac{\partial^{#1} {#2}}{\partial {#3}^{#1}}}}
\begin{document}
In text mode there is~\deriv{y}{x} and~\deriv[2]{y}{x}. In display mode there is
\[
  \deriv{y}{x}\ \textrm{and}\ \deriv[2]{y}{x}\rlap{.}
\]
\end{document}

The default <order> is empty, implying the first order partial derivative. If you want the default to be 2, modify the definition to read

\newcommand{\deriv}[3][2]{...}

Technically it is possible to use a macro with numbers in them, but the usage is much less intuitive than adding something like an optional argument (as given above). Here's an implementation that now allows you to use \nameuse{deriv2}{y}{x}:

\expandafter\def\csname deriv2\endcsname#1#2{%
  \ensuremath{\frac{\partial^2 {#1}}{\partial {#2}^2}}}
\makeatletter
\newcommand{\nameuse}[1]{\@nameuse{#1}}%
\makeatother

The optional argument beats this hands down.

Pass optional empty arguments in a newcommand down to another command with optional empty arguments in LaTeX

You can use \NewDocumentCommand.

\NewDocumentCommand{\hlc}{O{yellow}m}{\sethlcolor{#1}\hl{#2}}

\NewDocumentCommand{\hlcite}{oom}{%
  \hlc[green]{%
    \IfNoValueTF{#1}{% no optional argument
      \parencite{#3}%
    }{%
      \IfNoValueTF{#2}{% just one optional argument
        \parencite[#1]{#3}%
      }{% both optional arguments
        \parencite[#1][#2]{#3}%
      }%
    }%
  }% end of \hlc
}

Note that you don't want a space between \sethlcolor{#1} ad \hl{#2}.

Best Answer

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[Tex/LaTex] \newcommand gives errors in math mode (with or without arguments)

Pass optional empty arguments in a newcommand down to another command with optional empty arguments in LaTeX

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