Setlength \parskip with \baselineskip

Question

For me it does not work to specify a plus and minus in units of pt in the setlength option for \parskip with \baselineskip.

Why is that the case, what might be typical reasons, how can I specify some flexibility when I set \setlength{\parskip}{\baselineskip}?

Thanks.

Answer 1

You can coerce \baselineskip to be a <dimen> by multiplying it by 1 and then adding the stretch and shrink components:

\setlength{\parskip}{1\baselineskip plus 2pt minus 1pt}

or use \glueexpr:

\setlength{\parskip}{\glueexpr\baselineskip + 0pt plus 2pt minus 1pt}

The latter would preserve possible components in \baselineskip and add to them; the former would kill the stretch and shrink components in \baselineskip.