How to set a counter to double the value of another counter?

Question

The title says it. Lets have to counters:

\newcounter{myCount}
\newcounter{anotherCount}

I set myCount to some value for example 10

\setcounter{myCount}{10}

How do I set counter anotherCount to double the value of myCount? I have tried things like

\setcounter{anotherCount}{2\value{myCount}}

and

\setcounter{anotherCount}{2\themyCount}

but non of this works.

Answer 1

The 'official' LaTeX way (using only things documented in LaTeX: A Document Preparation System) is to use \addtocounter, as mentioned in a comment

\documentclass{article}
\newcounter{A}
\newcounter{B}
\begin{document}
\setcounter{A}{3}
\setcounter{B}{\value{A}}
\addtocounter{B}{\value{A}}

\arabic{A} and \arabic{B}
\end{document}

Loading the calc package (part of the core LaTeX2e system) allows

\documentclass{article}
\usepackage{calc}

\newcounter{A}
\newcounter{B}
\begin{document}
\setcounter{A}{3}
\setcounter{B}{2*\value{A}}

\arabic{A} and \arabic{B}
\end{document}

Of course, you can also use lower-level TeX or e-TeX constructs, as covered in the other answers.

Answer 2

\documentclass{minimal}
\begin{document}
\newcounter{A}    \newcounter{B}
\setcounter{A}{3} \setcounter{B}{\numexpr\theA*2\relax}

\theA\ and \theB

\end{document}

Answer 3

Don't forget that counter isn't same as length. Use commands \advance, \divide and \multiply to work with counters.

For example, this code will compute value of typographics sheets (run it in the end of document):

\newcount{\podp}
\newcount{\podpfr}
\podp=\c@page
\podpfr=\c@page
\divide\podp by 16
\multiply\podp by 100
\multiply\podpfr by 100
\divide\podpfr by 16
\advance\podpfr by -\podp
\divide\podp by 100
…
\hbox to 0pt{Формат $60\!\times\!84\;1/16$}\hfil Усл.печ.л.~%
{\the\podp.\ifnum\podpfr<10 0\fi\the\podpfr}\hfil