Inline Math in the end of the document

Question

Is there a way to get all the inline math ie., equations enclosed with $...$ and \(...\) in a TeX file should print in the end of the document like endfloat functionality.

Answer 1

In plain TeX, we can use \everymath primitive register:

\def\eqlist{}
\def\collectedequations{\everymath={}
   \ifx\eqlist\empty no equations\else \eqlist \fi}
\everymath={\savemath}
\def\savemath#1${#1$\global\addto\eqlist{$#1$\par}}
\long\def\addto#1#2{\expandafter\def\expandafter#1\expandafter{#1#2}}
A test $a^2=aa$ and $a^3=aaa$ and $a+b+c=42$.
\collectedequations
\bye

Answer 2

Beware of methods suggesting \everymath:

\def\eqlist{}
\def\collectedequations{\everymath={}
   \ifx\eqlist\empty no equations\else \eqlist \fi}
\everymath={\savemath}
\def\savemath#1${#1$\global\addto\eqlist{$#1$\par}}
\long\def\addto#1#2{\expandafter\def\expandafter#1\expandafter{#1#2}}
$0=0$
a\footnote{b}
\collectedequations
\bye

Running tex on this example raises the quite cryptic error message

Runaway argument?
! Paragraph ended before \next was complete.
<to be read again>
                   \par
l.11

Assuming LaTeX you can use \(...\) with a suitable redefinition.

\documentclass{article}
\ExplSyntaxOn
\seq_new:N \g__rampsmart_formulas_seq
\RenewDocumentCommand{(}{}
 {
  \rampsmart_collectmath:w
 }
\cs_new_protected:Npn \rampsmart_collectmath:w #1 )
 {
  \seq_gput_right:Nn \g__rampsmart_formulas_seq { $#1$ }
  $#1$
 }
\NewDocumentCommand{\printformulas}{+m}
 {
  \cs_set:Nn __rampsmart_collectmath_print:nn { #1 }
  \seq_map_indexed_function:NN \g__rampsmart_formulas_seq __rampsmart_collectmath_print:nn
 }
\ExplSyntaxOff
\begin{document}
\section{Text}
(0=0) is true; to the contrary, (0=1) is false.
[
x(yz)=x(yz)
]
\section{Formulas}
Here are all the formulas:
\printformulas{#1. #2\par}
\section{Again}
In a different format:
\begin{enumerate}
\printformulas{\item #2}
\end{enumerate}
\end{document}

The argument to \printformulas is the template to be used: #1 stands for the serial number and #2 for the actual formula.

Following Yiannis' invitation, here's an example of how one can use the two arguments in the template for getting hyperlinks.

\documentclass{article}
\usepackage{hyperref}
\ExplSyntaxOn
\seq_new:N \g__rampsmart_formulas_seq
\RenewDocumentCommand{(}{}
 {
  \rampsmart_collectmath:w
 }
\cs_new_protected:Npn \rampsmart_collectmath:w #1 )
 {
  \seq_gput_right:Nn \g__rampsmart_formulas_seq { $#1$ }
  \hypertarget{cf@\seq_count:N \g__rampsmart_formulas_seq}{$#1$}
 }
\NewDocumentCommand{\printformulas}{+m}
 {
  \cs_set:Nn __rampsmart_collectmath_print:nn { #1 }
  \seq_map_indexed_function:NN \g__rampsmart_formulas_seq __rampsmart_collectmath_print:nn
 }
\NewDocumentCommand{\formulalink}{mm}
 {
  \hyperlink{cf@#1}{#2}
 }
\ExplSyntaxOff
\begin{document}
\section{Text}
(0=0) is true. \newpage
To the contrary, (0=1) is false.
[
x(yz)=x(yz)
]
\section{Formulas}
Here are all the formulas:
\printformulas{#1. #2\par}
\section{Hyperlinks}
\begin{enumerate}
\printformulas{\item \formulalink{#1}{#2}}
\end{enumerate}
\end{document}

The target is given a name based on the current number of items in the sequence where we store the formulas, so we can use the index for defining the hyperlink.

Answer 3

Here is a short solution, works for the \(...\)

\documentclass{article}
\ExplSyntaxOn
\clist_new:N\inline_math_store_clist
\long\def\(#1\){\begingroup
\clist_put_right:Nn\inline_math_store_clist{#1}
$#1$
}%
\def\){\endgroup}%
\def\collectedequations{
\clist_map_inline:Nn\inline_math_store_clist{
  \math##1\endmath\par
}}  
\ExplSyntaxOff
\begin{document}
A test (a^2=aa) and (a^3=aaa) and ( a+b+c=42)
\collectedequations
\end{document}

Answer 4

Thanks @Wipet and @Yiannis your input really helped me put to find a solution on this request. Then, solution discussed by @Circumscribe from the link Automatically list all equations from document also helped to achieve the whole. I have supplied my code change below for LaTeX files.

\documentclass{article}

\usepackage{etoolbox}

\newbox\savedeqs
\newbox\inlinemath
\newbox\unnummath
\newbox\inlineparen
\newbox\unnumparen
\newwrite@mathfile

\newcommand\saveandprinteq[1]{%
\begingroup
\expandafter\let\csname @currenvir\expandafter\endcsname\csname listeq@@currenvir\endcsname
\expandafter\let\csname end@currenvir\expandafter\endcsname\csname listeq@end@currenvir\endcsname
\edef\listeq@temp{%
\noexpand\begin{@currenvir}%
\unexpanded{#1}%
\noexpand\end{@currenvir}%
}%
\savecounters@%
\global\setbox\savedeqs=\vbox{\unvbox\savedeqs\listeq@temp}%
\restorecounters@%
\listeq@temp%
\endgroup}

\newcommand*\listeqpatch[1]{% %% <- patches equation environment
\expandafter\let\csname listeq@#1\expandafter\endcsname\csname #1\endcsname
\expandafter\let\csname listeq@end#1\expandafter\endcsname\csname end#1\endcsname
\renewenvironment{#1}{\collect@body\saveandprinteq}{}}

\begingroup
\catcode`$=\active
\protected\gdef${@ifnextchar$@doubledollar@singledollar}
\protected\gdef@doubledollar$#1$${\edef\listueq@temp{\detokenize{$$#1$$}}%
\savecounters@%
\global\setbox\unnummath=\vbox{\unvbox\unnummath\listueq@temp}%
\restorecounters@%
\protected@write@mathfile{}{\listueq@temp}}
\protected\gdef@singledollar#1${\edef\listieq@temp{\detokenize{$#1$\par}}%
\savecounters@%
\global\setbox\inlinemath=\vbox{\unvbox\inlinemath\listieq@temp}%
\restorecounters@%
\protected@write@mathfile{}{\listieq@temp}}
\protected\gdef(#1){
\edef\listipeq@temp{\detokenize{$#1$\par}}%
\savecounters@%
\global\setbox\inlineparen=\vbox{\unvbox\inlineparen\listipeq@temp}%
\restorecounters@%
\protected@write@mathfile{}{\listipeq@temp}}%
\protected\gdef[#1]{
\edef\listupeq@temp{\detokenize{$$#1$$}}%
\savecounters@%
\global\setbox\unnumparen=\vbox{\unvbox\unnumparen\listupeq@temp}%
\restorecounters@%
\protected@write@mathfile{}{\listupeq@temp}}
\endgroup

\AtBeginDocument{%
\immediate\openout@mathfile=\jobname-MathFile.tex
\catcode`$=\active}

\newcommand\listofequations{%
\immediate\closeout@mathfile%
\catcode`$=3%
\clearpage%
\pagestyle{empty}%
\textbf{\Large List of Equations}\vskip10pt
\input \jobname-MathFile.tex%
\unvbox\savedeqs}

%% Patching equation environments
\listeqpatch{gather}
\listeqpatch{alignat}
\listeqpatch{xalignat}
\listeqpatch{align}
\listeqpatch{flalign}
\listeqpatch{equation}
\listeqpatch{eqnarray}
\listeqpatch{multline}
\listeqpatch{gather*}
\listeqpatch{alignat*}
\listeqpatch{xalignat*}
\listeqpatch{align*}
\listeqpatch{flalign*}
\listeqpatch{equation*}
\listeqpatch{eqnarray*}
\listeqpatch{multline*}

\begin{document}

$a+b=0$

\(c-d=0\)

$$a+b=0$$

\[c-d=0\]

\begin{equation}
a+b=0
\end{equation}

... ... ...

\listofequations

\end{document}