sum of two variables

Question

how can I make the sum of 2 variables in cm? Example: \y+ \n \x + \m

Thank in advance

Minimal coding:

\documentclass{article}
\usepackage[absolute,overlay]{textpos}
\usepackage{xcolor}

\newcommand*{\x}{0.5cm}
\newcommand*{\y}{2.0cm}
\newcommand*{\m}{1.5cm}
\newcommand*{\n}{2.5cm}

\begin{document}
\title{Texblock color}

\textblockcolour{cyan}
\begin{textblock*}{5cm}(2cm,10cm)
  123 

\end{textblock*}
\textblockcolour{red}
\begin{textblock*}{5cm}(\x,\y+\n)
  456 
\end{textblock*}

\textblockcolour{yellow}
\begin{textblock*}{5cm}(\x+\m,16cm)
  789
\end{textblock*}

\end{document}

Answer 1

I suggest not defining one-letter command, but to use a more semantic approach.

\documentclass{article}
\usepackage[absolute,overlay]{textpos}
\usepackage{xcolor}
\ExplSyntaxOn
\NewDocumentCommand{\definevar}{mm}
 {
  \tl_clear_new:c { l_forti_var_#1_tl }
  \tl_set:cn { l_forti_var_#1_tl } { #2 }
 }
\NewExpandableDocumentCommand{\usevar}{m}
 {
  \tl_use:c { l_forti_var_#1_tl }
 }
\ExplSyntaxOff
\definevar{x}{0.5cm}
\definevar{y}{2.0cm}
\definevar{m}{1.5cm}
\definevar{n}{2.5cm}
\begin{document}
\title{Texblock color}
\textblockcolour{cyan}
\begin{textblock}{5cm}(2cm,10cm)
  123 
\end{textblock}
\textblockcolour{red}
\begin{textblock}{5cm}(\usevar{x},\dimeval{\usevar{y}+\usevar{n}})
  456 
\end{textblock}
\textblockcolour{yellow}
\begin{textblock}{5cm}(\dimeval{\usevar{x}+\usevar{m}},16cm)
  789
\end{textblock}
\end{document}

You can still go the \newcommand way, with the same syntax with \dimeval to perform the operation, so like

\begin{textblock*}{5cm}(\x,\dimeval{\y+\n})

if you prefer the style I don't recommend.

Answer 2

Use calculator package.

\documentclass{article}
\usepackage{calculator}
\usepackage{amsmath}
\newcommand{\x}{0.5}
\newcommand{\y}{2}
\newcommand{\m}{1.5}
\newcommand{\n}{2.5}
\begin{document}
\ADD{\x}{\y}{\one}
\(\x\text{cm} + \y\text{cm} = \one\text{cm}\)
\ADD{\m}{\n}{\two}
And (\m\text{cm} + \n\text{cm} = \two\text{cm})
\end{document}