CarLaTeX
In the following MWE:
```
\documentclass{article}
\usepackage{tikz}
\begin{document}
\thispagestyle{empty}
\begin{tikzpicture}
\draw (0,0) to[in=180, out=0, looseness=.75] (3,3);
\draw[green] (0,0) -- (.25\textwidth,0);
\draw[red] (0,-3) to[in=180, out=0, looseness=.75] (.25\textwidth,0);
\end{tikzpicture}
\end{document}
```
the first two `\draw`s work, whereas the third gives this error:
```
<to be read again>
\textwidth
l.8 ...80, out=0, looseness=.75] (.25\textwidth,0)
;
The control sequence marked <to be read again> should
not appear between \csname and \endcsname.
Missing character: There is no 0 in font nullfont!
! Extra \endcsname.
\pgfutil@ifundefined ...@ifx \csname #1\endcsname
\relax
l.8 ...80, out=0, looseness=.75] (.25\textwidth,0)
;
I'm ignoring this, since I wasn't doing a \csname.
```
Why?