Declare command for both math and text mode: Spacing

Question

I want to create a command \points working in both math and text mode. Unfortunately I still have problems creating the correct (horizontal) spacing after several attempts. Here is my basic „setup“, where I am missing space before \points{3} inside math mode.

Code

\documentclass{article}

\usepackage{amsmath}
\usepackage{xparse}

\DeclareDocumentCommand \points { m } {\text{[#1\,P]}}

\begin{document}

Sentence end \points{1}. Between \points{2} words.

$x^2 + 9 = 0 \points{3}$

\end{document}

Result

Answer 1

Math mode eats up spaces, so you have to enforce one.

You can change the macro to:

\NewDocumentCommand \points { m } {\ifmmode\ \fi\text{[#1\,P]}}

or enforce the space when using the command:

$x^2 + 9 = 0\ \points{3}$

but not both, otherwise you'll get two spaces.

Also, notice that I replaced, following @egreg's remark, \DeclareDocumentCommand by \NewDocumentCommand.

\DeclareDocumentCommand has a behavior akin to \def regarding already defined commands. It will create the command no matter what, so you may be replacing an already existing macro with this.

\NewDocumentCommand, on the other hand, is equivalent to LaTeX's \newcommand; it will check if the command being created already exists and, if it does, an error will appear.

Answer 2

\documentclass{article}
\usepackage{amsmath}
\newcommand\points[1]{\ensuremath{\mathrel{[#1\,\mathrm{P}]}}}    
\begin{document}    
    Sentence end \points{1}. Between \points{2} words.

    $x^2 + 9 = 0 \points{3}$

\end{document}

Answer 3

If you add \ifmmode\text{\space} to the command, it will always insert a space in front if used in math mode. Also, I used \newcommand instead of \NewDocumentCommand since making a command that takes a single mandatory argument does not require the more advanced functionality of \NewDocumentCommand.

\documentclass{article}
\usepackage{amsmath}

\newcommand\points[1]{\relax\ifmmode\text{ }\fi\text{[#1\,P]}}

\begin{document}

Sentence end \points{1}. Between \points{2} words.

$x^2 + 9 = 0 \points{3}$

\end{document}