I want the 'equation number' that appears in the text to be different to the 'equation number' that appears in the equation. For example, if I have
\begin{equation}
a=b
\tag{1}
\reftag{2}
\label{eqn}
\end{equation}
\eqref{eqn}
Then the equation should have (1), but the reference is to (2). Is this possible?
Edit: Background
I am trying to make it so I can have two sub equations side by side. My current solution is as follows:
\newlength{\sbsseLl}
\newlength{\sbsseLr}
\newlength{\sbsseLe}
\newlength{\sbsseLle}
\newlength{\sbsseLre}
\newlength{\sbsseLt}
\newcommand{\sidebysidesubequations}[6]{%
% #1 reference label
% #2 left subequation
% #3 left label
% #4 midtext
% #5 right subequation
% #6 right label
%
%Setup the equations to be typed
\def\sbsseEl{#2}
\def\sbsseEr{\ifstrempty{#4}{#5}{\textrm{#4} \qquad #5}}
%Compute the width of the left and right side equations as inputted
\settowidth{\sbsseLl}{\begin{math}\displaystyle\sbsseEl\end{math}}
\settowidth{\sbsseLr}{\begin{math}\displaystyle\sbsseEr\end{math}}
\settowidth{\sbsseLt}{(\ref*{#1}a,b)}
%\setlength{\sbsseLt}{\sbsseLt+15mm}
%Compute the extra length to give to each
\setlength{\sbsseLe}{(\linewidth-\sbsseLl-\sbsseLr-\sbsseLt)/2}
\setlength{\sbsseLle}{\sbsseLl+\sbsseLe}
\setlength{\sbsseLre}{\sbsseLr+\sbsseLt+\sbsseLe}
%Construct table with these widths and place equations in cells
\noindent
\begin{subequations}\label{#1}
\begin{tabular}{@{}p{\sbsseLle}@{}p{\sbsseLre}@{}}%p{\sbsseLte}@{}}
\begin{equation}
\sbsseEl \vphantom{\sbsseEr}
\label{#3} \tag*{}
\end{equation}
\renewcommand\theequation{abc}\label{eqn:my}
&
\begin{equation}
\sbsseEr \vphantom{\sbsseEl}
\label{#6} \tag*{(\ref*{#1}a,b)}
\end{equation}
\end{tabular}
\end{subequations}
\newline
}
With this setup, I can write \sidebysidesubequations{eqn:all}{a=b}{eqn:left}{and}{c=d}{eqn:right} and get two equations formatted side by side with the equation number, e.g., (1a,b). However, \ref{eqn:left} gives an empty reference when it should be 1a, whilst \ref{eqn:right} gives the reference 1a,b when it should give 1b. What I would like to do is modify the referencing so that I can assign the correct label to each sub equation, and still have all the references together at the end of the line.
Edit 2: Minimal worked example
\documentclass{article}
\usepackage{amsmath}
\usepackage[hidelinks]{hyperref}
\usepackage{cleveref}
\usepackage{calc,etoolbox}
\newlength{\sbsseLl}
\newlength{\sbsseLr}
\newlength{\sbsseLe}
\newlength{\sbsseLle}
\newlength{\sbsseLre}
\newlength{\sbsseLt}
\newcommand{\sidebysidesubequations}[6]{%
% #1 reference label
% #2 left subequation
% #3 left label
% #4 midtext
% #5 right subequation
% #6 right label
%
%Setup the equations to be typed
\def\sbsseEl{#2}
\def\sbsseEr{\ifstrempty{#4}{#5}{\textrm{#4} \qquad #5}}
%Compute the width of the left and right side equations as inputted
\settowidth{\sbsseLl}{\begin{math}\displaystyle\sbsseEl\end{math}}
\settowidth{\sbsseLr}{\begin{math}\displaystyle\sbsseEr\end{math}}
\settowidth{\sbsseLt}{(\ref*{#1}a,b)}
%Compute the extra length to give to each
\setlength{\sbsseLe}{(\linewidth-\sbsseLl-\sbsseLr-\sbsseLt)/2}
\setlength{\sbsseLle}{\sbsseLl+\sbsseLe}
\setlength{\sbsseLre}{\sbsseLr+\sbsseLt+\sbsseLe}
%Construct table with these widths and place equations in cells
\noindent
\begin{subequations}\label{#1}
\begin{tabular}{@{}p{\sbsseLle}@{}p{\sbsseLre}@{}}%p{\sbsseLte}@{}}
\begin{equation}
\sbsseEl \vphantom{\sbsseEr}
\label{#3} \tag*{}
\end{equation}
&
\begin{equation}
\sbsseEr \vphantom{\sbsseEl}
\label{#6} \tag{\ref*{#1}a,b}
\end{equation}
\end{tabular}
\end{subequations}
\newline
}
\begin{document}
Here are my equations:
\sidebysidesubequations{eqn:all}{le=ft}{eqn:left}{and}{ri=ght}{eqn:right}
The overall system gets correctly referenced as `\cref{eqn:all}'.
However, the left equation gets incorrectly referenced as `\cref{eqn:left}', it should be `eq. (1a)',
similarly the right gets referenced as `\cref{eqn:right}', it should be `eq. (1b)'.
\end{document}
Edit 3: Fixed example using solution by Werner
\documentclass{article}
\usepackage{amsmath}
\usepackage[hidelinks]{hyperref}
\usepackage{cleveref}
\usepackage{calc,etoolbox}
\makeatletter
\newlength{\sbsseWl} %Width of left equation
\newlength{\sbsseWm} %Width of mid text
\newlength{\sbsseWr} %Width of right equation
\newlength{\sbsseWt} %Width of tag
\newlength{\sbsseWe} %Remaining width on line
\newlength{\sbsseWd} %Remaining width divided into pieces
\newcommand{\sidebysidesubequations}[6]{%
% #1 reference label
% #2 left subequation
% #3 left label
% #4 midtext
% #5 right subequation
% #6 right label
%Setup the equations to be typed
\def\sbsseEl{#2}
\def\sbsseEm{\textrm{#4}}
\def\sbsseEr{#5}
\def\sbsseEt{(\ref*{#1}a,b)}
%Compute the widths
\settowidth{\sbsseWl}{\begin{math}\displaystyle\sbsseEl\end{math}}
\settowidth{\sbsseWm}{\begin{math}\displaystyle\sbsseEm\end{math}}
\settowidth{\sbsseWr}{\begin{math}\displaystyle\sbsseEr\end{math}}
\settowidth{\sbsseWt}{\sbsseEt}
\setlength{\sbsseWe}{\linewidth-\sbsseWl-\sbsseWm-\sbsseWr-\sbsseWt}
%Beigin equation typesetting, with label for overall subequations
\begin{subequations}\ltx@label{{#1}}
\begin{displaymath}
%Left equation and label
\sbsseEl\refstepcounter{equation}\ltx@label{{#3}}
%Space, and midtext if any
\if\relax\detokenize{#4}\relax
\setlength{\sbsseWd}{\sbsseWe/3}
\hspace{\sbsseWd}
\else
\setlength{\sbsseWd}{\sbsseWe/4}
\hspace{\sbsseWd}\sbsseEm\hspace{\sbsseWd}
\fi
%Right equation and label
\sbsseEr\refstepcounter{equation}\ltx@label{{#6}}
%Tag
\tag*{\sbsseEt}
\end{displaymath}
\end{subequations}
}
\makeatother
\begin{document}
Here are my equations:
\sidebysidesubequations{eqn:all}{le=ft}{eqn:left}{and}{ri=ght}{eqn:right}
The overall system gets referenced as `\cref{eqn:all}', the left equation gets referenced as `\cref{eqn:left}', the right gets referenced as `\cref{eqn:right}'.
\end{document}
\sidebysidesubequations.