\documentclass[a4paper]{book}
\usepackage[T1]{fontenc}
\usepackage[french]{babel}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{exercise}
\ExplSyntaxOn
\NewDocumentCommand{\newtheoremx}{smomo}
{
\IfBooleanTF{#1}
{
\printthm_nonumber:nn { #2 } { #4 }
}
{
\printthm_number:nnnn { #2 } { #3 } { #4 } { #5 }
}
}
\cs_new_protected:Nn \printthm_nonumber:nn
{
\newtheorem{#1@inner}{#2}
\NewDocumentEnvironment{#1}{o+b}
{
% start the inner environment (without or with optional argument)
\tl_if_novalue:nTF { ##1 }
{ \begin{#1@inner} }
{ \begin{#1@inner}[##1] }
% typeset the statement
##2
% end the inner environment
\end{#1@inner}
% store the statement in a sequence variable, actually as
% four arguments as shown
\seq_gput_right:Nx \g_riccardo_theorems_seq
{
{ #1 } % name
{ } % number
\tl_if_novalue:nF { ##1 } { [\exp_not:n {##1}] } % attribution
{ \exp_not:n { ##2 } } % body
}
}{}
}
\cs_new_protected:Nn \printthm_number:nnnn
{
% * Let's duplicate the working of \newtheorem; \newtheoremx should
% be used for theorems that need to be listed
% * \newtheoremx{theorem}{Theorem} will actually do
% \newtheorem{theorem@inner}{Theorem} (honoring the usual optional arguments)
% * We also need a property list to store along with the theorem
% the one which it is subordinate to
\tl_if_novalue:nTF { #2 }
{
\tl_if_novalue:nTF { #4 }
{
\newtheorem{#1@inner}{#3}
}
{
\newtheorem{#1@inner}{#3}[#4]
}
% #1 is not subordinate, store the name itself
\prop_gput:Nnn \g_riccardo_theorems_prop { #1 } { #1 }
\seq_gput_right:Nn \g_riccardo_theorems_counters_seq { #1 }
}
{
\newtheorem{#1@inner}[#2@inner]{#3}
% #1 is subordinate to #2
\prop_gput:Nnn \g_riccardo_theorems_prop { #1 } { #2 }
}
% define a "grabbing" environment #1 with the usual features
\NewDocumentEnvironment{#1}{o+b}
{
% start the inner environment (without or with optional argument)
\tl_if_novalue:nTF { ##1 }
{ \begin{#1@inner} }
{ \begin{#1@inner}[##1] }
% save the statement number
\tl_gset:Nx \g__riccardo_theorems_number_tl { \use:c {@currentlabel} }
% typeset the statement
##2
% end the inner environment
\end{#1@inner}
% store the statement in a sequence variable, actually as
% four arguments as shown
\seq_gput_right:Nx \g_riccardo_theorems_seq
{
{ #1 } % name
{ \g__riccardo_theorems_number_tl } % number
\IfValueT{##1}{ [\exp_not:n { ##1 }] } % attribution
{ \exp_not:n { ##2 } } % body
}
}{}
}
% allocate the needed variables
\prop_new:N \g_riccardo_theorems_prop
\seq_new:N \g_riccardo_theorems_seq
\tl_new:N \g__riccardo_theorems_number_tl
\iow_new:N \g_riccardo_theorems_stream
\seq_new:N \g_riccardo_theorems_counters_seq
% print the stored theorems
\NewDocumentCommand{\printtheorems}{}
{
% we need a group where nullifying the action of \label
\group_begin:
\cs_set_eq:NN \label \use_none:n
% map the sequence, passing each item to the function that prints a theorem
\file_if_exist_input:n { \c_sys_jobname_str.thl }
% end the group
\group_end:
\seq_map_inline:Nn \g_riccardo_theorems_counters_seq
{
\setcounter{##1@inner}{0}
}
}
\cs_new_protected:Nn \riccardo_theorems_save:
{
\seq_map_function:NN \g_riccardo_theorems_seq __riccardo_theorems_save:n
}
\cs_new_protected:Nn __riccardo_theorems_save:n
{
\iow_now:Nn \g_riccardo_theorems_stream
{
\savedtheorem #1
}
}
\AtEndDocument
{
\iow_open:Nn \g_riccardo_theorems_stream { \c_sys_jobname_str.thl }
\riccardo_theorems_save:
\iow_close:N \g_riccardo_theorems_stream
}
\NewDocumentCommand{\savedtheorem}{smmom}
{
% redefine \the<statement>@inner to yield the stored number
% we use the property list to use the correct counter
% (for instance, in case of "lemma", <statement> will be "theorem"
\IfBooleanTF{#1}
{
\IfNoValueTF{#4}
{\begin{#2@inner}#5\end{#2@inner}}
{\begin{#2@inner}[#4]#5\end{#2@inner}}
}
{
\cs_set:cpn { the \prop_item:Nn \g_riccardo_theorems_prop {#2} @inner } { #3 }
\IfNoValueTF{#4}
{
% no attribution
\begin{#2@inner} #5 \end{#2@inner}
}
{
% attribution
\begin{#2@inner}[#4] #5 \end{#2@inner}
}
}
}
\ExplSyntaxOff
\newtheoremx{theorem}{Théorème}[chapter]
\newtheoremx{theorem}{Théorème}
\newtheoremx{proposition}[theorem]{Proposition}
\newtheoremx{corollary}[theorem]{Corollaire}
\newtheoremx{lemma}[theorem]{Lemme}
\begin{document}
\chapter{Pomme}
Bonjour
\begin{theorem}
Si alors
\end{theorem}
Bonjour
\begin{theorem}
Ssi
\end{theorem}
\begin{theorem}[Attribution]
$\Rightarrow$
\end{theorem}
\chapter{Banane}
\begin{corollary}
Donc
\end{corollary}
\begin{lemma}
Ainsi
\end{lemma}
\begin{Exercise}[difficulty=2]
\begin{theorem}[Théorème de Steiner]Whatever.\end{theorem}
\end{Exercise}
\chapter*{Théorèmes}
\printtheorems
\end{document}
\newtheoremx, not\newtheorem. However, the code doesn't cope with unnumbered theorems. A new version for this will appear shortly. – egreg Mar 23 '19 at 21:14