macrosoptional arguments
The recent release (June 2021) of the derivative package includes the command \odif which can be used to typeset differentials.
For instance, \odif[order={3}]{x} yields something like d^3x.
Because I am replacing the physics package, I would like to add a \newcommand which replaces \dd[3]{x} with \odif[order={3}]{x}.
I know that \newcommand{\dd}[1]{\odif{#1}} would replace \dd{x} with \odif{x} but I don't know how to handle the optional argument.
Try the new xparse package, which is built on top of LaTeX3. With this package you can specify arbitrary combinations of mandatory and optional arguments. This case would be as easy as
\DeclareDocumentCommand \sfsx { m m o } { \wrapper{#1}{#2}{#3} }
If you want to have your own default value, use O{value} instead of o.
Use expl3:
\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand{\myreplace}{m}
{
\tl_set:Nn \l__maxd_argument_tl { #1 }
\tl_replace_all:Nnn \l__maxd_argument_tl { - } { . }
\tl_use:N \l__maxd_argument_tl
}
\tl_new:N \l__maxd_argument_tl
\ExplSyntaxOff
\begin{document}
\myreplace{1-2-abc-345}
\end{document}
What's the advantage? You can easily generalize your command using the same idea.
\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand{\myreplace}{ O{} m }
{
\maxd_replace:nn { #1 } { #2 }
}
\tl_new:N \l__maxd_argument_tl
\cs_new_protected:Npn \maxd_replace:nn #1 #2
{
\group_begin:
\tl_set:Nn \l__maxd_argument_tl { #2 }
\keys_set:nn { maxd/replace } { #1 }
\tl_replace_all:NVV \l__maxd_argument_tl \l_maxd_search_tl \l_maxd_replace_tl
\tl_use:N \l__maxd_argument_tl
\group_end:
}
\cs_generate_variant:Nn \tl_replace_all:Nnn { NVV }
\keys_define:nn { maxd/replace }
{
search .tl_set:N = \l_maxd_search_tl,
search .initial:n = { - },
replace .tl_set:N = \l_maxd_replace_tl,
replace .initial:n = { . }
}
\ExplSyntaxOff
\begin{document}
\myreplace{1-2-abc-345}
\myreplace[replace=--]{1-2-abc-345}
\myreplace[search=2,replace=0]{1-2-abc-345}
\end{document}
Best Answer
You can supply a marker when the optional argument is empty to decide if there is an optional argument.
xparsehas a mechanism for this: