Perform simple calculations on user-defined variables

Question

In my document, I have a user-defined variable like:

 \newcommand{\MyNumber}{30}

Suppose, if I want to use a derivative of \MyNumber, it could be \MyNumber+10, 100-\MyNumber, 5*\MyNumber of \MyNumber/5, can that be done?

One step forward, if I have:

\newcommand{\MyNumberA}{30}

\newcommand{\MyNumberB}{60}

Can I use, \MyNumberA+\MyNumberB?

There are several solutions. For example, my package calculator. — Robert Fuster, Mar 23 '14 at 12:43
Possible duplicate: How can I define a mathematical function as a LaTeX macro? — Henri Menke, Mar 23 '14 at 13:01

score 10 · Accepted Answer · answered Mar 23 '14 at 13:12

10

You can use etex capabilities for simple calculations:

\numexpr (\MyNumberA + 2* \MyNumberN)/3 \relax `

computes a weighted means of \MyNumberA and \MyNumberB.

Similarly, you can do calculations with dimensions, using \dimexpr.

answered Mar 23 '14 at 13:12

Bernard

271,350

4

You can add that you have to add \the if you want to print the result. – karlkoeller Mar 23 '14 at 16:11
Thanks @karlkoeller, \the\numexpr (2 + 2) \relax even works within siunitx (e.g. \SI{\the\numexpr (2 + 2) \relax}{\meter}) – F1iX Aug 05 '20 at 08:59
How do I store the value in another variable? Should I write \newcommand{\MyNumberC}{\numexpr (\MyNumberA + 2* \MyNumberN)/3 \relax}? – Subhajit Paul Oct 08 '23 at 06:29

score 3 · Answer 2 · answered Mar 23 '14 at 13:06

You can do all of this using Plain TeX/LaTeX counters.

\documentclass{article}
\pagestyle{empty}% for cropping
\begin{document}
\obeylines%
\newcount\MyNumber%
\MyNumber=30%
\def\tp#1{\texttt{\string\MyNumber #1} =}%
\tp{} \the\MyNumber
\advance\MyNumber by 10\relax%
\tp{ + 10} \the\MyNumber
\multiply\MyNumber by 100\relax%
\tp{ * 100} \the\MyNumber

\medskip
Adding numbers:
\newcount\MyNumberA
\newcount\MyNumberB
\MyNumberA=30
\MyNumberB=60
\the\MyNumberA + \the\MyNumberB = \the\numexpr\MyNumberA + \MyNumberB\relax
\end{document}

Perform simple calculations on user-defined variables

2 Answers2

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