How to create two series of align equations in the same document?

Question

This question is similar to a previous question about how to create two series of numbered equations in the same document. However, the proposed solution doesn't work for my question, because it increments the counter once in the environment. Instead, I need a solution that works with the align environment. So, how can I work with two series of equation numbers using the align environment?

For example I need environments alignA and alignB that allow me to write:

\begin{alignA}
  x &= 2*y \\
    &= 3*z
\end{alignA}

\begin{alignB}
  u &= 4*v \\
    &= 5*w
\end{alignB}

That outputs equation numbers A1, A2, B1 and B2.

Answer 1

Here is more structured option via environment declaration

\documentclass{article}
\usepackage{amsmath}
\usepackage{etoolbox}

\makeatletter
\newcounter{qrr@oldeq}
\newcounter{qrr@oldsubeq}
\newcounter{qrr@realeq}

\newcounter{Bqrr@oldeq}
\newcounter{Bqrr@oldsubeq}
\newcounter{Bqrr@realeq}


\newenvironment{AlignA*}{% Consecutive subequations A
\setcounter{qrr@realeq}{\value{equation}}%
\let\theparentequation\theequation%
\patchcmd{\theparentequation}{equation}{parentequation}{}{}%
\setcounter{parentequation}{\numexpr\value{qrr@oldeq}-1}%
\setcounter{equation}{\value{qrr@oldsubeq}}%
\def\theequation{A-\arabic{equation}}%
\refstepcounter{parentequation}%
\ignorespaces
}{%
\setcounter{qrr@oldeq}{\value{parentequation}}%
\setcounter{qrr@oldsubeq}{\value{equation}}%
\setcounter{equation}{\value{qrr@realeq}}%
\ignorespacesafterend
}

\newenvironment{AlignA}{% Non consecutive subequations A
\refstepcounter{equation}%
\protected@edef\theparentequation{\theequation}%
\setcounter{parentequation}{\value{equation}}%
\setcounter{equation}{0}%
\def\theequation{A-\arabic{equation}}%
\ignorespaces
}{%
\setcounter{qrr@oldeq}{\value{parentequation}}%
\setcounter{qrr@oldsubeq}{\value{equation}}%
\setcounter{equation}{\value{parentequation}}%
\ignorespacesafterend
}

\newenvironment{AlignB}{% Non consecutive subequations B
\refstepcounter{equation}%
\protected@edef\theparentequation{\theequation}%
\setcounter{parentequation}{\value{equation}}%
\setcounter{equation}{0}%
\def\theequation{B-\arabic{equation}}%
\ignorespaces
}{%
\setcounter{Bqrr@oldeq}{\value{parentequation}}%
\setcounter{Bqrr@oldsubeq}{\value{equation}}%
\setcounter{equation}{\value{parentequation}}%
\ignorespacesafterend
}

\newenvironment{AlignB*}{% Consecutive subequations B
\setcounter{Bqrr@realeq}{\value{equation}}%
\let\theparentequation\theequation%
\patchcmd{\theparentequation}{equation}{parentequation}{}{}%
\setcounter{parentequation}{\numexpr\value{Bqrr@oldeq}-1}%
\setcounter{equation}{\value{Bqrr@oldsubeq}}%
\def\theequation{B-\arabic{equation}}%
\refstepcounter{parentequation}%
\ignorespaces
}{%
\setcounter{Bqrr@oldeq}{\value{parentequation}}%
\setcounter{Bqrr@oldsubeq}{\value{equation}}%
\setcounter{equation}{\value{qrr@realeq}}%
\ignorespacesafterend
}

\makeatother

\begin{document}


The AlignA environment goes from A-1 to A-n and if you use it again eq. counter resets
\begin{AlignA}
\begin{align}
\alpha\\
\beta\\
\gamma\\
\delta
\end{align}
\end{AlignA}
%\thesubA
The AlignB environment goes from B-1 to B-n and if you use it again eq. counter resets
\begin{AlignB}
\begin{align}
\alpha\\
\beta\\
\gamma
\end{align}
\end{AlignB}
The AlignA* environment goes from A-n to A-n+m and if you use it again eq. counter stay
\begin{AlignA*}
\begin{align}
\alpha\\
\beta\\
\gamma
\end{align}
\end{AlignA*}
 The AlignB* environment goes from B-n to B-n+m and if you use it again eq. counter stay
\begin{AlignB*}
\begin{align}
\alpha\\
\beta\\
\gamma
\end{align}
\end{AlignB*}
A normal Equation
\begin{equation}
\mbox{other equation}
\end{equation}


\end{document}

Answer 2

As I understand you first need to declare de environments "AlingA" and "AlingB" and a counter to them with \renewcomand

or try this (load ams math package)

\begin{subequations}
\renewcommand{\theequation}{A-\arabic{equation}}
\begin{equation}
A=y
\end{equation}
\begin{equation}
y=2 
\end{equation}
\end{subequations}
\setcounter{equation}{0} % reset to 0 equation counter
\begin{subequations}
\renewcommand{\theequation}{B-\arabic{equation}}
\begin{equation}
B=2y
\end{equation}
\begin{equation}
y=2 
\end{equation}
\end{subequations}