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I have a counter called LCount, which I want to use in some text, and i would like to be able to reference numbers that are relative to that counter. for example, I would like this LaTeX code:

For the regular languages: \begin{align*} &L_\theLCount = L((a|b^*)cc^*a^*(c|b^*)^*)\\\stepcounter{LCount} &L_\theLCount = L(ac^*c(a^*|b)^*)\stepcounter{LCount} \end{align*} If $L_\theLCount = L_{\theLCount-2} \cap L_{\theLCount-1}$, then:

to render like this:

enter image description here

if LCount has an initial value of 2. Is there a way of doing this? Should I be using something different other than counters? I know i can use \addtocounter a bunch of times and make the final line:

If $L_\theLCount = \addtocounter{LCount}{-2} L_\theLCount \cap \addtocounter{LCount}{1} L_\theLCount$\stepcounter{LCount}, then:

but that seems really clumsy and inefficient. Is there a better way?

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    The standard way would be to use refstepcounter and labels, but it seems that there is some clash with equation labelling... see also tex.stackexchange.com/questions/21300/… Commented Apr 27, 2016 at 7:33

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You can do something like this:

\makeatletter \newcount\tmpc@unter \newcount\LCount \LCount=2 \def\stepL{\global\advance\LCount1\relax} \def\theL{{\the\LCount}} \def\nextL{{\stepL\theL}} \def\refL#1{{\tmpc@unter=\LCount\advance\tmpc@unter#1\relax\the\tmpc@unter}} \makeatother \begin{document} $$L_\theL = L_\nextL + L_\nextL$$ and now: $$L_\refL{-2} = L_\refL{-1} + L_\theL$$ \end{document}

I.e. use temporal counter.

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An option is to use the standard way of \refstepcounter: 

\documentclass{article} \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \usepackage{amsmath} \newcounter{LCount} \begin{document} \stepcounter{LCount}\stepcounter{LCount} For the regular languages: \begin{equation} \refstepcounter{LCount}\label{first} L_\theLCount = L((a|b^*)cc^*a^*(c|b^*)^*) \end{equation} \[ \refstepcounter{LCount}\label{second} L_\theLCount = L(ac^*c(a^*|b)^*) \] \refstepcounter{LCount} If $L_\theLCount = L_{\ref{first}} \cap L_{\ref{second}}$, then: \end{document}

But beware that there will be problems (worth another question, I think) with amsmath and the counters used for equation numbering.

Output in standard article class

(BTW, post a complete MWE next time...)

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