Help with a \newcommand not working with autonum

Question

I am writing my thesis. To write math formulas I created the command \eq as follows.

\newcommand{\eq}[1]{
\begin{equation}
  \begin{split}
  #1 
  \end{split}
\end{equation}} 

However, now I want to use cleveref together with autonum.

I think, however, that this is not possible due to the way I defined the command \eq. Here goes a minimal working example.

\documentclass{minimal}
\usepackage{amsmath}
\usepackage{cleveref}
\usepackage{autonum}

\newcommand{\eq}[1]{ 
\begin{equation}
  \begin{split}
  #1 
  \end{split}
\end{equation}} 

\begin{document}

Without my command:\\

This is an equation
\begin{equation}\label{eq_1}
\begin{split}
    1+1 &=2,\\
    2+2 &=4.
\end{split}
\end{equation}

This is another
\begin{equation}\label{eq_2}
    1+1=3.
\end{equation}

Only \cref{eq_1} is correct.\\

\noindent\rule{8cm}{0.4pt}

But with my command:\\

This is an equation
\eq{\label{Eq_1}
  1+1 &=2,\\
  2+2 &=4.
}

This is another
\eq{\label{Eq_2}
  1+1=3.
}

Only \cref{Eq_1} is correct.

\end{document}

The output does not show the number of the equation Eq_1.

So, I think the mistake is that the label of \eq is within \split, and autonum has problems understanding that. If I comment the package autonum everything goes fine but of course all eq's get numbered.

I have a lot of equations, so I do not want to change each of them.

Can any body suggest a way to just change the definition of the command \eq so that autonum works?

Answer 1

This is so wrong; you're obfuscating your code for minimal gain.

Anyway, here's the way without changing your input.

\documentclass{article}
\usepackage{amsmath}
\usepackage{cleveref}
\usepackage{autonum}

\makeatletter
\newcommand{\eq}[1]{%
  \begingroup
  \findlabel@{#1}%
  \begin{equation}
  \put@label
  \begin{split}
  \pre@label\post@label
  \end{split}
  \end{equation}%
  \endgroup
}
\def\put@label{}
\def\findlabel@#1{\findlabel@i#1\label\@nil}
\def\findlabel@i#1\label#2\@nil{%
  \def\pre@label{#1}
  \if\relax\detokenize{#2}\relax
    \def\post@label{}%
  \else
    \findlabel@ii#2\@nil
  \fi
}
\def\findlabel@ii#1#2\@nil{%
  \def\put@label{\label{#1}}\findlabel@iii#2%
}
\def\findlabel@iii#1\label{%
  \def\post@label{#1}%
}
\makeatother

\begin{document}

Without my command:

This is an equation
\begin{equation}\label{eq_1}
\begin{split}
    1+1 &=2,\\
    2+2 &=4.
\end{split}
\end{equation}

This is another
\begin{equation}\label{eq_2}
    1+1=3.
\end{equation}

Only \cref{eq_1} is correct.

\noindent\rule{8cm}{0.4pt}

But with my command:

This is an equation
\eq{\label{Eq_1}
  1+1 &=2,\\
  2+2 &=4.
}

This is another
\eq{\label{Eq_2}
  1+1=3.
}

Now \cref{Eq_1} is correct.

\end{document}

The code looks for a \label command, isolating what comes before it and after it, then building the environment and supplying the various bits in the correct position (\label outside split).

Answer 2

If you define \eq as you did, then the label goes inside the split environment, so your labels are not recognized.

A correct definition could be

\newcommand{\eq}[2]{%
\begin{equation}\label{#1}%
  \begin{split}%
  #2%
  \end{split}%
\end{equation}}

to be used in this way (the first argument is the label, the second is the body):

\eq{Eq_1}{
  1+1 &=2,\\
  2+2 &=4.
}

MWE:

\documentclass{minimal}
\usepackage{amsmath}
\usepackage{cleveref}
\usepackage{autonum}

\newcommand{\eq}[2]{%
\begin{equation}\label{#1}%
  \begin{split}%
  #2%
  \end{split}%
\end{equation}}

\begin{document}

Without my command:\bigskip

This is an equation
\begin{equation}\label{eq_1}
\begin{split}
    1+1 &=2,\\
    2+2 &=4.
\end{split}
\end{equation}

This is another
\begin{equation}\label{eq_2}
    1+1=3.
\end{equation}

Only \cref{eq_1} is correct.\bigskip

\noindent\rule{8cm}{0.4pt}\bigskip

But with my command:\bigskip

This is an equation
\eq{Eq_1}{
  1+1 &=2,\\
  2+2 &=4.
}

This is another
\eq{Eq_2}{
  1+1=3.
}

Only \cref{Eq_1} is correct.

\end{document} 

Output:

A remark: never use \\ to terminate a line... See When to use \par and when \\, or blank lines for reference.