Define numeric variable in terms of another variable
You can use xparse
and xfp
(the latter allows computations on the fly):
\documentclass{article}
\usepackage{xparse,xfp}
\ExplSyntaxOn
\NewDocumentCommand{\defineconstant}{mm}
{
\cs_new:Npx #1 { \fp_eval:n { #2 } }
}
\ExplSyntaxOff
\begin{document}
\defineconstant{\constantA}{0.25}
\defineconstant{\constantB}{1-\constantA}
\defineconstant{\constantC}{round(sqrt(\constantA),2)+\constantB/2}
The value of \verb|\constantA| is \constantA
The value of \verb|\constantB| is \constantB
The value of \verb|\constantC| is \constantC
\fpeval{round(\constantA-\constantC+exp(2),4)}
\end{document}
You can use pgf
package for this. Instead TeX primitive \def
one need use \pgfmathsetmacro
\documentclass{article}
\usepackage{pgf}
\begin{document}
\pgfmathsetmacro{\first}{0.25}
\pgfmathsetmacro{\second}{1-\first}
The value of \verb|\first| is \first
The value of \verb|\second| is \second
\end{document}