Consider the following example:
\newlength{\textsize}
\makeatletter
\setlength{\textsize}{\f@size pt}
\makeatother
\setlength{\parskip}{12pt plus 1pt} % WORKS
\setlength{\parskip}{\textsize plus 1pt} % FAIL
How to make the failing line work?
Which means: how to set a length to another length plus and/or minus other values?
Best Answer
LaTeX lengths are skip registers so
\textsize
is a complete glue specification and can not take a furtherplus
component.1\textwidth
coerces this to a dimen, discarding any plus and minus components, so you can add a new plus component.