Replace . (period) by , (comma) in numbers

Question

I pass a bunch of numbers into a custom command defined via \newcommand{\mycmd}[1]{...}:

\mycmd{1.12}
\mycmd{5.32}

\mycmd uses the number to draw a certain figure. On top of that, I would like to print the number in \mycmd, but with a comma instead of a decimal point: 1,12, 5,32.

Any suggestion would be appreciated.

Answer 1

I'm sure the siunitx package is the way to go because it will catch all corner cases. Out of curiosity, here is a simple solution that uses TeX's pattern matching capabilities.

\documentclass{minimal}
\def\usecomma#1.#2{#1,#2}
\newcommand\mycmd[1]{\usecomma #1}
\begin{document}
    \obeylines
    1.12 $\to$ \mycmd{1.12}
    5.32 $\to$ \mycmd{5.32}
\end{document}

Note that it won't work if you pass an argument that has no dot, like \mycmd{2}. Is this too simple and there is something else that I have overlooked?

Answer 2

This can be done using the siunitx package. Use the \num macro with the output-decimal-marker={,} option. The option can also be set globally using \sisetup{output-decimal-marker={,}}.

\documentclass{article}

\usepackage{siunitx}

\begin{document}

\num[output-decimal-marker={,}]{123.45}

\end{document}

Answer 3

There's a number of possible solutions; two of them: 1) Use the isonums package:

\documentclass{article}
\usepackage{isonums}
\newcommand\mycmd[1]{$#1$}

\begin{document}
\mycmd{5.32}
\end{document}

2) If you are using babel, you could use the spanish option and select it to typeset your number (the spanish option, by default uses the comma as the decimal separator):

\documentclass{article}
\usepackage[spanish,english]{babel}

\newcommand\mycmd[1]{$\selectlanguage{spanish}#1$}

\begin{document}
\mycmd{5.32}
\end{document}

Of course, if spanish is the only option for babel, then \selectlanguage{spanish} is superfluous.

Answer 4

You can just use the numprint package:

\documentclass{article}
\usepackage{numprint}

\begin{document}
    \obeylines
    1.12 $\to$ \numprint{1.12}
    5.32 $\to$ \numprint{5.32}
\end{document}