How to robustly store bits of text for later use












5















I'm trying to write myself a package, similar to the exercise package, so I can prepare problem sets for my students. I wish to delay the output of problems and/or solutions until a suitable place in the document has been reached. I have something that sort of works but it's kind of clunky. For example, this works pretty well:



usepackage{environ}
NewEnviron{testb}{globalexpandafterletcsname barendcsnameBODY}


I use csname because the names are dynamically generated. This doesn't work so well if the command is anything other than BODY. For example, if I do letbar{BODY}, latex has an aneurysm (it binds bar to just {).



There is an alternate way of doing this, which is:



NewEnviron{testc}{globalexpandafteredefcsname fooendcsname{BODY}}


This sort of works. The following thing works:
begin{testc}hiend{testc}, but this gives LaTeX an aneurysm: begin{testc}bf hiend{testc}. (The error message is incomplete). I tried to debug it myself but I get hopelessly tangled up in packages that I don't understand. If you do it with tiny instead of bf you get the wildly different LaTeX error message: ! TeX capacity exceeded, sorry [input stack size=5000].



How can I squirrel away for later, not just BODY, but some sophisticated combination of BODY and other stuff, while having it robust to what's between the begin and end?



Edit: ok multiple solutions below










share|improve this question









New contributor




Sébastien Loisel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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  • 1





    Why not use def? let does what it should do: use the the next token.

    – TeXnician
    Mar 19 at 13:02











  • If you mean this: NewEnviron{testc}{globalexpandafterdefcsname fooendcsname{BODY}}, I get: ! Undefined control sequence. foo ->BODY

    – Sébastien Loisel
    Mar 19 at 13:09






  • 1





    I'm not sure why you don't like globalexpandafterletcsname barendcsnameBODY: it's entirely normal TeX.

    – Joseph Wright
    Mar 19 at 13:31











  • I started writing a class file to prepare conference programmes using the same sort of "save text for later" features. github.com/scmbradley/schedule I have just realised that this was six years ago. My god. Six years!?

    – Seamus
    Mar 19 at 13:47











  • You should definitely use let with BODY, def with anything whose definition doesn't change, and edef with things that do change (and you don't mind expanding them).

    – John Kormylo
    Mar 19 at 16:05


















5















I'm trying to write myself a package, similar to the exercise package, so I can prepare problem sets for my students. I wish to delay the output of problems and/or solutions until a suitable place in the document has been reached. I have something that sort of works but it's kind of clunky. For example, this works pretty well:



usepackage{environ}
NewEnviron{testb}{globalexpandafterletcsname barendcsnameBODY}


I use csname because the names are dynamically generated. This doesn't work so well if the command is anything other than BODY. For example, if I do letbar{BODY}, latex has an aneurysm (it binds bar to just {).



There is an alternate way of doing this, which is:



NewEnviron{testc}{globalexpandafteredefcsname fooendcsname{BODY}}


This sort of works. The following thing works:
begin{testc}hiend{testc}, but this gives LaTeX an aneurysm: begin{testc}bf hiend{testc}. (The error message is incomplete). I tried to debug it myself but I get hopelessly tangled up in packages that I don't understand. If you do it with tiny instead of bf you get the wildly different LaTeX error message: ! TeX capacity exceeded, sorry [input stack size=5000].



How can I squirrel away for later, not just BODY, but some sophisticated combination of BODY and other stuff, while having it robust to what's between the begin and end?



Edit: ok multiple solutions below










share|improve this question









New contributor




Sébastien Loisel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
















  • 1





    Why not use def? let does what it should do: use the the next token.

    – TeXnician
    Mar 19 at 13:02











  • If you mean this: NewEnviron{testc}{globalexpandafterdefcsname fooendcsname{BODY}}, I get: ! Undefined control sequence. foo ->BODY

    – Sébastien Loisel
    Mar 19 at 13:09






  • 1





    I'm not sure why you don't like globalexpandafterletcsname barendcsnameBODY: it's entirely normal TeX.

    – Joseph Wright
    Mar 19 at 13:31











  • I started writing a class file to prepare conference programmes using the same sort of "save text for later" features. github.com/scmbradley/schedule I have just realised that this was six years ago. My god. Six years!?

    – Seamus
    Mar 19 at 13:47











  • You should definitely use let with BODY, def with anything whose definition doesn't change, and edef with things that do change (and you don't mind expanding them).

    – John Kormylo
    Mar 19 at 16:05
















5












5








5








I'm trying to write myself a package, similar to the exercise package, so I can prepare problem sets for my students. I wish to delay the output of problems and/or solutions until a suitable place in the document has been reached. I have something that sort of works but it's kind of clunky. For example, this works pretty well:



usepackage{environ}
NewEnviron{testb}{globalexpandafterletcsname barendcsnameBODY}


I use csname because the names are dynamically generated. This doesn't work so well if the command is anything other than BODY. For example, if I do letbar{BODY}, latex has an aneurysm (it binds bar to just {).



There is an alternate way of doing this, which is:



NewEnviron{testc}{globalexpandafteredefcsname fooendcsname{BODY}}


This sort of works. The following thing works:
begin{testc}hiend{testc}, but this gives LaTeX an aneurysm: begin{testc}bf hiend{testc}. (The error message is incomplete). I tried to debug it myself but I get hopelessly tangled up in packages that I don't understand. If you do it with tiny instead of bf you get the wildly different LaTeX error message: ! TeX capacity exceeded, sorry [input stack size=5000].



How can I squirrel away for later, not just BODY, but some sophisticated combination of BODY and other stuff, while having it robust to what's between the begin and end?



Edit: ok multiple solutions below










share|improve this question









New contributor




Sébastien Loisel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.












I'm trying to write myself a package, similar to the exercise package, so I can prepare problem sets for my students. I wish to delay the output of problems and/or solutions until a suitable place in the document has been reached. I have something that sort of works but it's kind of clunky. For example, this works pretty well:



usepackage{environ}
NewEnviron{testb}{globalexpandafterletcsname barendcsnameBODY}


I use csname because the names are dynamically generated. This doesn't work so well if the command is anything other than BODY. For example, if I do letbar{BODY}, latex has an aneurysm (it binds bar to just {).



There is an alternate way of doing this, which is:



NewEnviron{testc}{globalexpandafteredefcsname fooendcsname{BODY}}


This sort of works. The following thing works:
begin{testc}hiend{testc}, but this gives LaTeX an aneurysm: begin{testc}bf hiend{testc}. (The error message is incomplete). I tried to debug it myself but I get hopelessly tangled up in packages that I don't understand. If you do it with tiny instead of bf you get the wildly different LaTeX error message: ! TeX capacity exceeded, sorry [input stack size=5000].



How can I squirrel away for later, not just BODY, but some sophisticated combination of BODY and other stuff, while having it robust to what's between the begin and end?



Edit: ok multiple solutions below







macros environments






share|improve this question









New contributor




Sébastien Loisel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











share|improve this question









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Sébastien Loisel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









share|improve this question




share|improve this question








edited Mar 19 at 15:40







Sébastien Loisel













New contributor




Sébastien Loisel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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asked Mar 19 at 12:59









Sébastien LoiselSébastien Loisel

1284




1284




New contributor




Sébastien Loisel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.





New contributor





Sébastien Loisel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






Sébastien Loisel is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.








  • 1





    Why not use def? let does what it should do: use the the next token.

    – TeXnician
    Mar 19 at 13:02











  • If you mean this: NewEnviron{testc}{globalexpandafterdefcsname fooendcsname{BODY}}, I get: ! Undefined control sequence. foo ->BODY

    – Sébastien Loisel
    Mar 19 at 13:09






  • 1





    I'm not sure why you don't like globalexpandafterletcsname barendcsnameBODY: it's entirely normal TeX.

    – Joseph Wright
    Mar 19 at 13:31











  • I started writing a class file to prepare conference programmes using the same sort of "save text for later" features. github.com/scmbradley/schedule I have just realised that this was six years ago. My god. Six years!?

    – Seamus
    Mar 19 at 13:47











  • You should definitely use let with BODY, def with anything whose definition doesn't change, and edef with things that do change (and you don't mind expanding them).

    – John Kormylo
    Mar 19 at 16:05
















  • 1





    Why not use def? let does what it should do: use the the next token.

    – TeXnician
    Mar 19 at 13:02











  • If you mean this: NewEnviron{testc}{globalexpandafterdefcsname fooendcsname{BODY}}, I get: ! Undefined control sequence. foo ->BODY

    – Sébastien Loisel
    Mar 19 at 13:09






  • 1





    I'm not sure why you don't like globalexpandafterletcsname barendcsnameBODY: it's entirely normal TeX.

    – Joseph Wright
    Mar 19 at 13:31











  • I started writing a class file to prepare conference programmes using the same sort of "save text for later" features. github.com/scmbradley/schedule I have just realised that this was six years ago. My god. Six years!?

    – Seamus
    Mar 19 at 13:47











  • You should definitely use let with BODY, def with anything whose definition doesn't change, and edef with things that do change (and you don't mind expanding them).

    – John Kormylo
    Mar 19 at 16:05










1




1





Why not use def? let does what it should do: use the the next token.

– TeXnician
Mar 19 at 13:02





Why not use def? let does what it should do: use the the next token.

– TeXnician
Mar 19 at 13:02













If you mean this: NewEnviron{testc}{globalexpandafterdefcsname fooendcsname{BODY}}, I get: ! Undefined control sequence. foo ->BODY

– Sébastien Loisel
Mar 19 at 13:09





If you mean this: NewEnviron{testc}{globalexpandafterdefcsname fooendcsname{BODY}}, I get: ! Undefined control sequence. foo ->BODY

– Sébastien Loisel
Mar 19 at 13:09




1




1





I'm not sure why you don't like globalexpandafterletcsname barendcsnameBODY: it's entirely normal TeX.

– Joseph Wright
Mar 19 at 13:31





I'm not sure why you don't like globalexpandafterletcsname barendcsnameBODY: it's entirely normal TeX.

– Joseph Wright
Mar 19 at 13:31













I started writing a class file to prepare conference programmes using the same sort of "save text for later" features. github.com/scmbradley/schedule I have just realised that this was six years ago. My god. Six years!?

– Seamus
Mar 19 at 13:47





I started writing a class file to prepare conference programmes using the same sort of "save text for later" features. github.com/scmbradley/schedule I have just realised that this was six years ago. My god. Six years!?

– Seamus
Mar 19 at 13:47













You should definitely use let with BODY, def with anything whose definition doesn't change, and edef with things that do change (and you don't mind expanding them).

– John Kormylo
Mar 19 at 16:05







You should definitely use let with BODY, def with anything whose definition doesn't change, and edef with things that do change (and you don't mind expanding them).

– John Kormylo
Mar 19 at 16:05












3 Answers
3






active

oldest

votes


















5














With unexpanded you can avoid worrying about protected@xdef.



documentclass{article}
usepackage{environ}

NewEnviron{exercise}{%
xdefsavedexercises{%
unexpandedexpandafter{savedexercises}%
noexpandbegin{printedexercise}%
unexpandedexpandafter{BODY}%
noexpandend{printedexercise}%
}%
}
newcommand{printexercises}{%
savedexercises
gdefsavedexercises{}%
}
newcommand{savedexercises}{}

newtheorem{printedexercise}{Exercise}

begin{document}

Here we talk about addition and show that $1+1=2$.

begin{exercise}
Compute $1+2$
end{exercise}

Here we talk about integrals.

begin{exercise}
Compute the following integrals:
begin{itemize}
item $displaystyleint_0^x e^{-t^2},dt$

item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
end{itemize}
end{exercise}

Now we can print the exercises.

printexercises

end{document}


I used newtheorem just for the example.



enter image description here



With xparse released 2019-03-05 or later:



documentclass{article}
usepackage{xparse}

ExplSyntaxOn

NewDocumentEnvironment{exercise}{+b}
{
tl_gput_right:Nn g_loisel_exercises_tl
{
begin{printedexercise}
#1
end{printedexercise}
}
}{}

NewDocumentCommand{printexercises}{}
{
tl_use:N g_loisel_exercises_tl
tl_gclear:N g_loisel_exercises_tl
}

tl_new:N g_loisel_exercises_tl

ExplSyntaxOff

newtheorem{printedexercise}{Exercise}

begin{document}

Here we talk about addition and show that $1+1=2$.

begin{exercise}
Compute $1+2$
end{exercise}

Here we talk about integrals.

begin{exercise}
Compute the following integrals:
begin{itemize}
item $displaystyleint_0^x e^{-t^2},dt$

item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
end{itemize}
end{exercise}

Now we can print the exercises.

printexercises

end{document}





share|improve this answer
























  • Oh this is good

    – Sébastien Loisel
    Mar 19 at 15:40



















6














If you want BODY to be saved then add stuff dynamically, you are likely best using two macros:



documentclass{article}
usepackage{environ}
NewEnviron{testb}{%
globalexpandafterletcsname barendcsnameBODY
expandafterxdefcsname barplusendcsname{%
expandafternoexpandcsname barendcsname
noexpandbf Hi
}%
}
begin{document}

begin{testb}
bfseries
Hi
end{testb}
showbarplus
end{document}


If you want to avoid using BODY you could use xparse



documentclass{article}
usepackage{xparse}
NewDocumentEnvironment{testb}{+b}{expandaftergdefcsname barendcsname{#1}}{}
begin{document}

begin{testb}
bfseries
Hi
end{testb}
showbar
end{document}





share|improve this answer


























  • This needs TL'19 or up-to-date MiKTeX: this is a new feature in xparse.

    – Joseph Wright
    Mar 19 at 13:34











  • Ah, thanks for this. By the way, I just tried this: NewEnviron{testc}{expandafterprotected@xdefcsname fooendcsname{BODY}} , and it seems to work. Is there any situation where this would break again?

    – Sébastien Loisel
    Mar 19 at 14:42











  • @SébastienLoisel Well if you have anything that's not LaTeX2e robust, yes, but that is nowadays quite a low risk.

    – Joseph Wright
    Mar 19 at 14:43











  • What's an example of something not LaTeX2e robust?

    – Sébastien Loisel
    Mar 19 at 15:04











  • Nevermind, I tried with begin{itemize}...end{itemize} and it broke.

    – Sébastien Loisel
    Mar 19 at 15:14



















0














A trick for triggering expansion is using romannumeral:



When due to romannumeral (La)TeX does gather together a sequence of digits trailed by a space as the number which it has to convert, expandable tokens get expanded.



When in the end a number is gathered together which is not positive, as the result of the conversion (La)TeX will not deliver any token at all.



Thus one can nicely (ab?)use romannumeral for triggering a lot of expansion-work and flipping-arguments-around-work as long as one ensures that in the end romannumeral will not find a positive number.



Here is a variant of egreg's answer which does with romannumeral and exchange instead of xdef and unexpanded.



documentclass{article}
usepackage{environ}

newcommandexchange[2]{#2#1}

NewEnviron{exercise}{%
expandaftergdefexpandaftersavedexercisesexpandafter{%
romannumeral0expandafterexchangeexpandafter{BODY}{%
exchange{ }{expandafter}savedexercises
begin{printedexercise}%
}%
end{printedexercise}%
}%
}
newcommand{printexercises}{%
savedexercises
gdefsavedexercises{}%
}
newcommand{savedexercises}{}

newtheorem{printedexercise}{Exercise}

begin{document}

Here we talk about addition and show that $1+1=2$.

begin{exercise}
Compute $1+2$
end{exercise}

Here we talk about integrals.

begin{exercise}
Compute the following integrals:
begin{itemize}
item $displaystyleint_0^x e^{-t^2},dt$

item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
end{itemize}
end{exercise}

Now we can print the exercises.

printexercises

end{document}


enter image description here



If you wish to wrap the name of the macro that is to be defined into csname..endcsname, i.e., if you wish to use csname savedexercisesendcsname rather than savedexercises, you can take advantage of the fact that (La)TeX does expand expandable tokens while due to csname gathering the name of a control sequence token and hereby searching for the matching endcsname:



documentclass{article}
usepackage{environ}

newcommandexchange[2]{#2#1}

NewEnviron{exercise}{%
expandaftergdefcsname savedexercisesexpandafterendcsnameexpandafter{%
romannumeral0expandafterexchangeexpandafter{BODY}{%
exchange{ }{expandafterexpandafterexpandafter}csname savedexercisesendcsname
begin{printedexercise}%
}%
end{printedexercise}%
}%
}
newcommand{printexercises}{%
csname savedexercisesendcsname
expandaftergdefcsname savedexercisesendcsname{}%
}
expandafternewcommandexpandafter{csname savedexercisesendcsname}{}

newtheorem{printedexercise}{Exercise}

begin{document}

Here we talk about addition and show that $1+1=2$.

begin{exercise}
Compute $1+2$
end{exercise}

Here we talk about integrals.

begin{exercise}
Compute the following integrals:
begin{itemize}
item $displaystyleint_0^x e^{-t^2},dt$

item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
end{itemize}
end{exercise}

Now we can print the exercises.

printexercises

end{document}


enter image description here



Be aware that with the approaches presented by now you cannot use printexercises for having exercises occur in arbitrary places. You can have exercises occur only in places of the document which in the source correspond to places behind the exercise-environments.



Perhaps an environment which does read its content under verbatim-catcode-régime for unexpanded-writing it to .aux-file in a way where from the .aux-file it gets read back under verbatim-catcode-régime also for defining a macro where scantokens will be applied to, and thus some sort of re-implementation of the label-ref-mechanism or of the tableofcontents-mechanism for verbatimized stuff might make it possible to make exercises printable throughout the entire document.



Implementing such a mechanism might be a nice challenge. But before taking that into consideration at all, exact information is needed on the intended usage and the desired "user-interface", i.e., what additional things you wish to be able to specify in which ways, etc, ...






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    3 Answers
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    3 Answers
    3






    active

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    active

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    active

    oldest

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    5














    With unexpanded you can avoid worrying about protected@xdef.



    documentclass{article}
    usepackage{environ}

    NewEnviron{exercise}{%
    xdefsavedexercises{%
    unexpandedexpandafter{savedexercises}%
    noexpandbegin{printedexercise}%
    unexpandedexpandafter{BODY}%
    noexpandend{printedexercise}%
    }%
    }
    newcommand{printexercises}{%
    savedexercises
    gdefsavedexercises{}%
    }
    newcommand{savedexercises}{}

    newtheorem{printedexercise}{Exercise}

    begin{document}

    Here we talk about addition and show that $1+1=2$.

    begin{exercise}
    Compute $1+2$
    end{exercise}

    Here we talk about integrals.

    begin{exercise}
    Compute the following integrals:
    begin{itemize}
    item $displaystyleint_0^x e^{-t^2},dt$

    item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
    end{itemize}
    end{exercise}

    Now we can print the exercises.

    printexercises

    end{document}


    I used newtheorem just for the example.



    enter image description here



    With xparse released 2019-03-05 or later:



    documentclass{article}
    usepackage{xparse}

    ExplSyntaxOn

    NewDocumentEnvironment{exercise}{+b}
    {
    tl_gput_right:Nn g_loisel_exercises_tl
    {
    begin{printedexercise}
    #1
    end{printedexercise}
    }
    }{}

    NewDocumentCommand{printexercises}{}
    {
    tl_use:N g_loisel_exercises_tl
    tl_gclear:N g_loisel_exercises_tl
    }

    tl_new:N g_loisel_exercises_tl

    ExplSyntaxOff

    newtheorem{printedexercise}{Exercise}

    begin{document}

    Here we talk about addition and show that $1+1=2$.

    begin{exercise}
    Compute $1+2$
    end{exercise}

    Here we talk about integrals.

    begin{exercise}
    Compute the following integrals:
    begin{itemize}
    item $displaystyleint_0^x e^{-t^2},dt$

    item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
    end{itemize}
    end{exercise}

    Now we can print the exercises.

    printexercises

    end{document}





    share|improve this answer
























    • Oh this is good

      – Sébastien Loisel
      Mar 19 at 15:40
















    5














    With unexpanded you can avoid worrying about protected@xdef.



    documentclass{article}
    usepackage{environ}

    NewEnviron{exercise}{%
    xdefsavedexercises{%
    unexpandedexpandafter{savedexercises}%
    noexpandbegin{printedexercise}%
    unexpandedexpandafter{BODY}%
    noexpandend{printedexercise}%
    }%
    }
    newcommand{printexercises}{%
    savedexercises
    gdefsavedexercises{}%
    }
    newcommand{savedexercises}{}

    newtheorem{printedexercise}{Exercise}

    begin{document}

    Here we talk about addition and show that $1+1=2$.

    begin{exercise}
    Compute $1+2$
    end{exercise}

    Here we talk about integrals.

    begin{exercise}
    Compute the following integrals:
    begin{itemize}
    item $displaystyleint_0^x e^{-t^2},dt$

    item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
    end{itemize}
    end{exercise}

    Now we can print the exercises.

    printexercises

    end{document}


    I used newtheorem just for the example.



    enter image description here



    With xparse released 2019-03-05 or later:



    documentclass{article}
    usepackage{xparse}

    ExplSyntaxOn

    NewDocumentEnvironment{exercise}{+b}
    {
    tl_gput_right:Nn g_loisel_exercises_tl
    {
    begin{printedexercise}
    #1
    end{printedexercise}
    }
    }{}

    NewDocumentCommand{printexercises}{}
    {
    tl_use:N g_loisel_exercises_tl
    tl_gclear:N g_loisel_exercises_tl
    }

    tl_new:N g_loisel_exercises_tl

    ExplSyntaxOff

    newtheorem{printedexercise}{Exercise}

    begin{document}

    Here we talk about addition and show that $1+1=2$.

    begin{exercise}
    Compute $1+2$
    end{exercise}

    Here we talk about integrals.

    begin{exercise}
    Compute the following integrals:
    begin{itemize}
    item $displaystyleint_0^x e^{-t^2},dt$

    item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
    end{itemize}
    end{exercise}

    Now we can print the exercises.

    printexercises

    end{document}





    share|improve this answer
























    • Oh this is good

      – Sébastien Loisel
      Mar 19 at 15:40














    5












    5








    5







    With unexpanded you can avoid worrying about protected@xdef.



    documentclass{article}
    usepackage{environ}

    NewEnviron{exercise}{%
    xdefsavedexercises{%
    unexpandedexpandafter{savedexercises}%
    noexpandbegin{printedexercise}%
    unexpandedexpandafter{BODY}%
    noexpandend{printedexercise}%
    }%
    }
    newcommand{printexercises}{%
    savedexercises
    gdefsavedexercises{}%
    }
    newcommand{savedexercises}{}

    newtheorem{printedexercise}{Exercise}

    begin{document}

    Here we talk about addition and show that $1+1=2$.

    begin{exercise}
    Compute $1+2$
    end{exercise}

    Here we talk about integrals.

    begin{exercise}
    Compute the following integrals:
    begin{itemize}
    item $displaystyleint_0^x e^{-t^2},dt$

    item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
    end{itemize}
    end{exercise}

    Now we can print the exercises.

    printexercises

    end{document}


    I used newtheorem just for the example.



    enter image description here



    With xparse released 2019-03-05 or later:



    documentclass{article}
    usepackage{xparse}

    ExplSyntaxOn

    NewDocumentEnvironment{exercise}{+b}
    {
    tl_gput_right:Nn g_loisel_exercises_tl
    {
    begin{printedexercise}
    #1
    end{printedexercise}
    }
    }{}

    NewDocumentCommand{printexercises}{}
    {
    tl_use:N g_loisel_exercises_tl
    tl_gclear:N g_loisel_exercises_tl
    }

    tl_new:N g_loisel_exercises_tl

    ExplSyntaxOff

    newtheorem{printedexercise}{Exercise}

    begin{document}

    Here we talk about addition and show that $1+1=2$.

    begin{exercise}
    Compute $1+2$
    end{exercise}

    Here we talk about integrals.

    begin{exercise}
    Compute the following integrals:
    begin{itemize}
    item $displaystyleint_0^x e^{-t^2},dt$

    item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
    end{itemize}
    end{exercise}

    Now we can print the exercises.

    printexercises

    end{document}





    share|improve this answer













    With unexpanded you can avoid worrying about protected@xdef.



    documentclass{article}
    usepackage{environ}

    NewEnviron{exercise}{%
    xdefsavedexercises{%
    unexpandedexpandafter{savedexercises}%
    noexpandbegin{printedexercise}%
    unexpandedexpandafter{BODY}%
    noexpandend{printedexercise}%
    }%
    }
    newcommand{printexercises}{%
    savedexercises
    gdefsavedexercises{}%
    }
    newcommand{savedexercises}{}

    newtheorem{printedexercise}{Exercise}

    begin{document}

    Here we talk about addition and show that $1+1=2$.

    begin{exercise}
    Compute $1+2$
    end{exercise}

    Here we talk about integrals.

    begin{exercise}
    Compute the following integrals:
    begin{itemize}
    item $displaystyleint_0^x e^{-t^2},dt$

    item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
    end{itemize}
    end{exercise}

    Now we can print the exercises.

    printexercises

    end{document}


    I used newtheorem just for the example.



    enter image description here



    With xparse released 2019-03-05 or later:



    documentclass{article}
    usepackage{xparse}

    ExplSyntaxOn

    NewDocumentEnvironment{exercise}{+b}
    {
    tl_gput_right:Nn g_loisel_exercises_tl
    {
    begin{printedexercise}
    #1
    end{printedexercise}
    }
    }{}

    NewDocumentCommand{printexercises}{}
    {
    tl_use:N g_loisel_exercises_tl
    tl_gclear:N g_loisel_exercises_tl
    }

    tl_new:N g_loisel_exercises_tl

    ExplSyntaxOff

    newtheorem{printedexercise}{Exercise}

    begin{document}

    Here we talk about addition and show that $1+1=2$.

    begin{exercise}
    Compute $1+2$
    end{exercise}

    Here we talk about integrals.

    begin{exercise}
    Compute the following integrals:
    begin{itemize}
    item $displaystyleint_0^x e^{-t^2},dt$

    item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
    end{itemize}
    end{exercise}

    Now we can print the exercises.

    printexercises

    end{document}






    share|improve this answer












    share|improve this answer



    share|improve this answer










    answered Mar 19 at 15:34









    egregegreg

    728k8819253235




    728k8819253235













    • Oh this is good

      – Sébastien Loisel
      Mar 19 at 15:40



















    • Oh this is good

      – Sébastien Loisel
      Mar 19 at 15:40

















    Oh this is good

    – Sébastien Loisel
    Mar 19 at 15:40





    Oh this is good

    – Sébastien Loisel
    Mar 19 at 15:40











    6














    If you want BODY to be saved then add stuff dynamically, you are likely best using two macros:



    documentclass{article}
    usepackage{environ}
    NewEnviron{testb}{%
    globalexpandafterletcsname barendcsnameBODY
    expandafterxdefcsname barplusendcsname{%
    expandafternoexpandcsname barendcsname
    noexpandbf Hi
    }%
    }
    begin{document}

    begin{testb}
    bfseries
    Hi
    end{testb}
    showbarplus
    end{document}


    If you want to avoid using BODY you could use xparse



    documentclass{article}
    usepackage{xparse}
    NewDocumentEnvironment{testb}{+b}{expandaftergdefcsname barendcsname{#1}}{}
    begin{document}

    begin{testb}
    bfseries
    Hi
    end{testb}
    showbar
    end{document}





    share|improve this answer


























    • This needs TL'19 or up-to-date MiKTeX: this is a new feature in xparse.

      – Joseph Wright
      Mar 19 at 13:34











    • Ah, thanks for this. By the way, I just tried this: NewEnviron{testc}{expandafterprotected@xdefcsname fooendcsname{BODY}} , and it seems to work. Is there any situation where this would break again?

      – Sébastien Loisel
      Mar 19 at 14:42











    • @SébastienLoisel Well if you have anything that's not LaTeX2e robust, yes, but that is nowadays quite a low risk.

      – Joseph Wright
      Mar 19 at 14:43











    • What's an example of something not LaTeX2e robust?

      – Sébastien Loisel
      Mar 19 at 15:04











    • Nevermind, I tried with begin{itemize}...end{itemize} and it broke.

      – Sébastien Loisel
      Mar 19 at 15:14
















    6














    If you want BODY to be saved then add stuff dynamically, you are likely best using two macros:



    documentclass{article}
    usepackage{environ}
    NewEnviron{testb}{%
    globalexpandafterletcsname barendcsnameBODY
    expandafterxdefcsname barplusendcsname{%
    expandafternoexpandcsname barendcsname
    noexpandbf Hi
    }%
    }
    begin{document}

    begin{testb}
    bfseries
    Hi
    end{testb}
    showbarplus
    end{document}


    If you want to avoid using BODY you could use xparse



    documentclass{article}
    usepackage{xparse}
    NewDocumentEnvironment{testb}{+b}{expandaftergdefcsname barendcsname{#1}}{}
    begin{document}

    begin{testb}
    bfseries
    Hi
    end{testb}
    showbar
    end{document}





    share|improve this answer


























    • This needs TL'19 or up-to-date MiKTeX: this is a new feature in xparse.

      – Joseph Wright
      Mar 19 at 13:34











    • Ah, thanks for this. By the way, I just tried this: NewEnviron{testc}{expandafterprotected@xdefcsname fooendcsname{BODY}} , and it seems to work. Is there any situation where this would break again?

      – Sébastien Loisel
      Mar 19 at 14:42











    • @SébastienLoisel Well if you have anything that's not LaTeX2e robust, yes, but that is nowadays quite a low risk.

      – Joseph Wright
      Mar 19 at 14:43











    • What's an example of something not LaTeX2e robust?

      – Sébastien Loisel
      Mar 19 at 15:04











    • Nevermind, I tried with begin{itemize}...end{itemize} and it broke.

      – Sébastien Loisel
      Mar 19 at 15:14














    6












    6








    6







    If you want BODY to be saved then add stuff dynamically, you are likely best using two macros:



    documentclass{article}
    usepackage{environ}
    NewEnviron{testb}{%
    globalexpandafterletcsname barendcsnameBODY
    expandafterxdefcsname barplusendcsname{%
    expandafternoexpandcsname barendcsname
    noexpandbf Hi
    }%
    }
    begin{document}

    begin{testb}
    bfseries
    Hi
    end{testb}
    showbarplus
    end{document}


    If you want to avoid using BODY you could use xparse



    documentclass{article}
    usepackage{xparse}
    NewDocumentEnvironment{testb}{+b}{expandaftergdefcsname barendcsname{#1}}{}
    begin{document}

    begin{testb}
    bfseries
    Hi
    end{testb}
    showbar
    end{document}





    share|improve this answer















    If you want BODY to be saved then add stuff dynamically, you are likely best using two macros:



    documentclass{article}
    usepackage{environ}
    NewEnviron{testb}{%
    globalexpandafterletcsname barendcsnameBODY
    expandafterxdefcsname barplusendcsname{%
    expandafternoexpandcsname barendcsname
    noexpandbf Hi
    }%
    }
    begin{document}

    begin{testb}
    bfseries
    Hi
    end{testb}
    showbarplus
    end{document}


    If you want to avoid using BODY you could use xparse



    documentclass{article}
    usepackage{xparse}
    NewDocumentEnvironment{testb}{+b}{expandaftergdefcsname barendcsname{#1}}{}
    begin{document}

    begin{testb}
    bfseries
    Hi
    end{testb}
    showbar
    end{document}






    share|improve this answer














    share|improve this answer



    share|improve this answer








    edited Mar 19 at 13:40

























    answered Mar 19 at 13:34









    Joseph WrightJoseph Wright

    205k23562890




    205k23562890













    • This needs TL'19 or up-to-date MiKTeX: this is a new feature in xparse.

      – Joseph Wright
      Mar 19 at 13:34











    • Ah, thanks for this. By the way, I just tried this: NewEnviron{testc}{expandafterprotected@xdefcsname fooendcsname{BODY}} , and it seems to work. Is there any situation where this would break again?

      – Sébastien Loisel
      Mar 19 at 14:42











    • @SébastienLoisel Well if you have anything that's not LaTeX2e robust, yes, but that is nowadays quite a low risk.

      – Joseph Wright
      Mar 19 at 14:43











    • What's an example of something not LaTeX2e robust?

      – Sébastien Loisel
      Mar 19 at 15:04











    • Nevermind, I tried with begin{itemize}...end{itemize} and it broke.

      – Sébastien Loisel
      Mar 19 at 15:14



















    • This needs TL'19 or up-to-date MiKTeX: this is a new feature in xparse.

      – Joseph Wright
      Mar 19 at 13:34











    • Ah, thanks for this. By the way, I just tried this: NewEnviron{testc}{expandafterprotected@xdefcsname fooendcsname{BODY}} , and it seems to work. Is there any situation where this would break again?

      – Sébastien Loisel
      Mar 19 at 14:42











    • @SébastienLoisel Well if you have anything that's not LaTeX2e robust, yes, but that is nowadays quite a low risk.

      – Joseph Wright
      Mar 19 at 14:43











    • What's an example of something not LaTeX2e robust?

      – Sébastien Loisel
      Mar 19 at 15:04











    • Nevermind, I tried with begin{itemize}...end{itemize} and it broke.

      – Sébastien Loisel
      Mar 19 at 15:14

















    This needs TL'19 or up-to-date MiKTeX: this is a new feature in xparse.

    – Joseph Wright
    Mar 19 at 13:34





    This needs TL'19 or up-to-date MiKTeX: this is a new feature in xparse.

    – Joseph Wright
    Mar 19 at 13:34













    Ah, thanks for this. By the way, I just tried this: NewEnviron{testc}{expandafterprotected@xdefcsname fooendcsname{BODY}} , and it seems to work. Is there any situation where this would break again?

    – Sébastien Loisel
    Mar 19 at 14:42





    Ah, thanks for this. By the way, I just tried this: NewEnviron{testc}{expandafterprotected@xdefcsname fooendcsname{BODY}} , and it seems to work. Is there any situation where this would break again?

    – Sébastien Loisel
    Mar 19 at 14:42













    @SébastienLoisel Well if you have anything that's not LaTeX2e robust, yes, but that is nowadays quite a low risk.

    – Joseph Wright
    Mar 19 at 14:43





    @SébastienLoisel Well if you have anything that's not LaTeX2e robust, yes, but that is nowadays quite a low risk.

    – Joseph Wright
    Mar 19 at 14:43













    What's an example of something not LaTeX2e robust?

    – Sébastien Loisel
    Mar 19 at 15:04





    What's an example of something not LaTeX2e robust?

    – Sébastien Loisel
    Mar 19 at 15:04













    Nevermind, I tried with begin{itemize}...end{itemize} and it broke.

    – Sébastien Loisel
    Mar 19 at 15:14





    Nevermind, I tried with begin{itemize}...end{itemize} and it broke.

    – Sébastien Loisel
    Mar 19 at 15:14











    0














    A trick for triggering expansion is using romannumeral:



    When due to romannumeral (La)TeX does gather together a sequence of digits trailed by a space as the number which it has to convert, expandable tokens get expanded.



    When in the end a number is gathered together which is not positive, as the result of the conversion (La)TeX will not deliver any token at all.



    Thus one can nicely (ab?)use romannumeral for triggering a lot of expansion-work and flipping-arguments-around-work as long as one ensures that in the end romannumeral will not find a positive number.



    Here is a variant of egreg's answer which does with romannumeral and exchange instead of xdef and unexpanded.



    documentclass{article}
    usepackage{environ}

    newcommandexchange[2]{#2#1}

    NewEnviron{exercise}{%
    expandaftergdefexpandaftersavedexercisesexpandafter{%
    romannumeral0expandafterexchangeexpandafter{BODY}{%
    exchange{ }{expandafter}savedexercises
    begin{printedexercise}%
    }%
    end{printedexercise}%
    }%
    }
    newcommand{printexercises}{%
    savedexercises
    gdefsavedexercises{}%
    }
    newcommand{savedexercises}{}

    newtheorem{printedexercise}{Exercise}

    begin{document}

    Here we talk about addition and show that $1+1=2$.

    begin{exercise}
    Compute $1+2$
    end{exercise}

    Here we talk about integrals.

    begin{exercise}
    Compute the following integrals:
    begin{itemize}
    item $displaystyleint_0^x e^{-t^2},dt$

    item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
    end{itemize}
    end{exercise}

    Now we can print the exercises.

    printexercises

    end{document}


    enter image description here



    If you wish to wrap the name of the macro that is to be defined into csname..endcsname, i.e., if you wish to use csname savedexercisesendcsname rather than savedexercises, you can take advantage of the fact that (La)TeX does expand expandable tokens while due to csname gathering the name of a control sequence token and hereby searching for the matching endcsname:



    documentclass{article}
    usepackage{environ}

    newcommandexchange[2]{#2#1}

    NewEnviron{exercise}{%
    expandaftergdefcsname savedexercisesexpandafterendcsnameexpandafter{%
    romannumeral0expandafterexchangeexpandafter{BODY}{%
    exchange{ }{expandafterexpandafterexpandafter}csname savedexercisesendcsname
    begin{printedexercise}%
    }%
    end{printedexercise}%
    }%
    }
    newcommand{printexercises}{%
    csname savedexercisesendcsname
    expandaftergdefcsname savedexercisesendcsname{}%
    }
    expandafternewcommandexpandafter{csname savedexercisesendcsname}{}

    newtheorem{printedexercise}{Exercise}

    begin{document}

    Here we talk about addition and show that $1+1=2$.

    begin{exercise}
    Compute $1+2$
    end{exercise}

    Here we talk about integrals.

    begin{exercise}
    Compute the following integrals:
    begin{itemize}
    item $displaystyleint_0^x e^{-t^2},dt$

    item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
    end{itemize}
    end{exercise}

    Now we can print the exercises.

    printexercises

    end{document}


    enter image description here



    Be aware that with the approaches presented by now you cannot use printexercises for having exercises occur in arbitrary places. You can have exercises occur only in places of the document which in the source correspond to places behind the exercise-environments.



    Perhaps an environment which does read its content under verbatim-catcode-régime for unexpanded-writing it to .aux-file in a way where from the .aux-file it gets read back under verbatim-catcode-régime also for defining a macro where scantokens will be applied to, and thus some sort of re-implementation of the label-ref-mechanism or of the tableofcontents-mechanism for verbatimized stuff might make it possible to make exercises printable throughout the entire document.



    Implementing such a mechanism might be a nice challenge. But before taking that into consideration at all, exact information is needed on the intended usage and the desired "user-interface", i.e., what additional things you wish to be able to specify in which ways, etc, ...






    share|improve this answer




























      0














      A trick for triggering expansion is using romannumeral:



      When due to romannumeral (La)TeX does gather together a sequence of digits trailed by a space as the number which it has to convert, expandable tokens get expanded.



      When in the end a number is gathered together which is not positive, as the result of the conversion (La)TeX will not deliver any token at all.



      Thus one can nicely (ab?)use romannumeral for triggering a lot of expansion-work and flipping-arguments-around-work as long as one ensures that in the end romannumeral will not find a positive number.



      Here is a variant of egreg's answer which does with romannumeral and exchange instead of xdef and unexpanded.



      documentclass{article}
      usepackage{environ}

      newcommandexchange[2]{#2#1}

      NewEnviron{exercise}{%
      expandaftergdefexpandaftersavedexercisesexpandafter{%
      romannumeral0expandafterexchangeexpandafter{BODY}{%
      exchange{ }{expandafter}savedexercises
      begin{printedexercise}%
      }%
      end{printedexercise}%
      }%
      }
      newcommand{printexercises}{%
      savedexercises
      gdefsavedexercises{}%
      }
      newcommand{savedexercises}{}

      newtheorem{printedexercise}{Exercise}

      begin{document}

      Here we talk about addition and show that $1+1=2$.

      begin{exercise}
      Compute $1+2$
      end{exercise}

      Here we talk about integrals.

      begin{exercise}
      Compute the following integrals:
      begin{itemize}
      item $displaystyleint_0^x e^{-t^2},dt$

      item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
      end{itemize}
      end{exercise}

      Now we can print the exercises.

      printexercises

      end{document}


      enter image description here



      If you wish to wrap the name of the macro that is to be defined into csname..endcsname, i.e., if you wish to use csname savedexercisesendcsname rather than savedexercises, you can take advantage of the fact that (La)TeX does expand expandable tokens while due to csname gathering the name of a control sequence token and hereby searching for the matching endcsname:



      documentclass{article}
      usepackage{environ}

      newcommandexchange[2]{#2#1}

      NewEnviron{exercise}{%
      expandaftergdefcsname savedexercisesexpandafterendcsnameexpandafter{%
      romannumeral0expandafterexchangeexpandafter{BODY}{%
      exchange{ }{expandafterexpandafterexpandafter}csname savedexercisesendcsname
      begin{printedexercise}%
      }%
      end{printedexercise}%
      }%
      }
      newcommand{printexercises}{%
      csname savedexercisesendcsname
      expandaftergdefcsname savedexercisesendcsname{}%
      }
      expandafternewcommandexpandafter{csname savedexercisesendcsname}{}

      newtheorem{printedexercise}{Exercise}

      begin{document}

      Here we talk about addition and show that $1+1=2$.

      begin{exercise}
      Compute $1+2$
      end{exercise}

      Here we talk about integrals.

      begin{exercise}
      Compute the following integrals:
      begin{itemize}
      item $displaystyleint_0^x e^{-t^2},dt$

      item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
      end{itemize}
      end{exercise}

      Now we can print the exercises.

      printexercises

      end{document}


      enter image description here



      Be aware that with the approaches presented by now you cannot use printexercises for having exercises occur in arbitrary places. You can have exercises occur only in places of the document which in the source correspond to places behind the exercise-environments.



      Perhaps an environment which does read its content under verbatim-catcode-régime for unexpanded-writing it to .aux-file in a way where from the .aux-file it gets read back under verbatim-catcode-régime also for defining a macro where scantokens will be applied to, and thus some sort of re-implementation of the label-ref-mechanism or of the tableofcontents-mechanism for verbatimized stuff might make it possible to make exercises printable throughout the entire document.



      Implementing such a mechanism might be a nice challenge. But before taking that into consideration at all, exact information is needed on the intended usage and the desired "user-interface", i.e., what additional things you wish to be able to specify in which ways, etc, ...






      share|improve this answer


























        0












        0








        0







        A trick for triggering expansion is using romannumeral:



        When due to romannumeral (La)TeX does gather together a sequence of digits trailed by a space as the number which it has to convert, expandable tokens get expanded.



        When in the end a number is gathered together which is not positive, as the result of the conversion (La)TeX will not deliver any token at all.



        Thus one can nicely (ab?)use romannumeral for triggering a lot of expansion-work and flipping-arguments-around-work as long as one ensures that in the end romannumeral will not find a positive number.



        Here is a variant of egreg's answer which does with romannumeral and exchange instead of xdef and unexpanded.



        documentclass{article}
        usepackage{environ}

        newcommandexchange[2]{#2#1}

        NewEnviron{exercise}{%
        expandaftergdefexpandaftersavedexercisesexpandafter{%
        romannumeral0expandafterexchangeexpandafter{BODY}{%
        exchange{ }{expandafter}savedexercises
        begin{printedexercise}%
        }%
        end{printedexercise}%
        }%
        }
        newcommand{printexercises}{%
        savedexercises
        gdefsavedexercises{}%
        }
        newcommand{savedexercises}{}

        newtheorem{printedexercise}{Exercise}

        begin{document}

        Here we talk about addition and show that $1+1=2$.

        begin{exercise}
        Compute $1+2$
        end{exercise}

        Here we talk about integrals.

        begin{exercise}
        Compute the following integrals:
        begin{itemize}
        item $displaystyleint_0^x e^{-t^2},dt$

        item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
        end{itemize}
        end{exercise}

        Now we can print the exercises.

        printexercises

        end{document}


        enter image description here



        If you wish to wrap the name of the macro that is to be defined into csname..endcsname, i.e., if you wish to use csname savedexercisesendcsname rather than savedexercises, you can take advantage of the fact that (La)TeX does expand expandable tokens while due to csname gathering the name of a control sequence token and hereby searching for the matching endcsname:



        documentclass{article}
        usepackage{environ}

        newcommandexchange[2]{#2#1}

        NewEnviron{exercise}{%
        expandaftergdefcsname savedexercisesexpandafterendcsnameexpandafter{%
        romannumeral0expandafterexchangeexpandafter{BODY}{%
        exchange{ }{expandafterexpandafterexpandafter}csname savedexercisesendcsname
        begin{printedexercise}%
        }%
        end{printedexercise}%
        }%
        }
        newcommand{printexercises}{%
        csname savedexercisesendcsname
        expandaftergdefcsname savedexercisesendcsname{}%
        }
        expandafternewcommandexpandafter{csname savedexercisesendcsname}{}

        newtheorem{printedexercise}{Exercise}

        begin{document}

        Here we talk about addition and show that $1+1=2$.

        begin{exercise}
        Compute $1+2$
        end{exercise}

        Here we talk about integrals.

        begin{exercise}
        Compute the following integrals:
        begin{itemize}
        item $displaystyleint_0^x e^{-t^2},dt$

        item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
        end{itemize}
        end{exercise}

        Now we can print the exercises.

        printexercises

        end{document}


        enter image description here



        Be aware that with the approaches presented by now you cannot use printexercises for having exercises occur in arbitrary places. You can have exercises occur only in places of the document which in the source correspond to places behind the exercise-environments.



        Perhaps an environment which does read its content under verbatim-catcode-régime for unexpanded-writing it to .aux-file in a way where from the .aux-file it gets read back under verbatim-catcode-régime also for defining a macro where scantokens will be applied to, and thus some sort of re-implementation of the label-ref-mechanism or of the tableofcontents-mechanism for verbatimized stuff might make it possible to make exercises printable throughout the entire document.



        Implementing such a mechanism might be a nice challenge. But before taking that into consideration at all, exact information is needed on the intended usage and the desired "user-interface", i.e., what additional things you wish to be able to specify in which ways, etc, ...






        share|improve this answer













        A trick for triggering expansion is using romannumeral:



        When due to romannumeral (La)TeX does gather together a sequence of digits trailed by a space as the number which it has to convert, expandable tokens get expanded.



        When in the end a number is gathered together which is not positive, as the result of the conversion (La)TeX will not deliver any token at all.



        Thus one can nicely (ab?)use romannumeral for triggering a lot of expansion-work and flipping-arguments-around-work as long as one ensures that in the end romannumeral will not find a positive number.



        Here is a variant of egreg's answer which does with romannumeral and exchange instead of xdef and unexpanded.



        documentclass{article}
        usepackage{environ}

        newcommandexchange[2]{#2#1}

        NewEnviron{exercise}{%
        expandaftergdefexpandaftersavedexercisesexpandafter{%
        romannumeral0expandafterexchangeexpandafter{BODY}{%
        exchange{ }{expandafter}savedexercises
        begin{printedexercise}%
        }%
        end{printedexercise}%
        }%
        }
        newcommand{printexercises}{%
        savedexercises
        gdefsavedexercises{}%
        }
        newcommand{savedexercises}{}

        newtheorem{printedexercise}{Exercise}

        begin{document}

        Here we talk about addition and show that $1+1=2$.

        begin{exercise}
        Compute $1+2$
        end{exercise}

        Here we talk about integrals.

        begin{exercise}
        Compute the following integrals:
        begin{itemize}
        item $displaystyleint_0^x e^{-t^2},dt$

        item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
        end{itemize}
        end{exercise}

        Now we can print the exercises.

        printexercises

        end{document}


        enter image description here



        If you wish to wrap the name of the macro that is to be defined into csname..endcsname, i.e., if you wish to use csname savedexercisesendcsname rather than savedexercises, you can take advantage of the fact that (La)TeX does expand expandable tokens while due to csname gathering the name of a control sequence token and hereby searching for the matching endcsname:



        documentclass{article}
        usepackage{environ}

        newcommandexchange[2]{#2#1}

        NewEnviron{exercise}{%
        expandaftergdefcsname savedexercisesexpandafterendcsnameexpandafter{%
        romannumeral0expandafterexchangeexpandafter{BODY}{%
        exchange{ }{expandafterexpandafterexpandafter}csname savedexercisesendcsname
        begin{printedexercise}%
        }%
        end{printedexercise}%
        }%
        }
        newcommand{printexercises}{%
        csname savedexercisesendcsname
        expandaftergdefcsname savedexercisesendcsname{}%
        }
        expandafternewcommandexpandafter{csname savedexercisesendcsname}{}

        newtheorem{printedexercise}{Exercise}

        begin{document}

        Here we talk about addition and show that $1+1=2$.

        begin{exercise}
        Compute $1+2$
        end{exercise}

        Here we talk about integrals.

        begin{exercise}
        Compute the following integrals:
        begin{itemize}
        item $displaystyleint_0^x e^{-t^2},dt$

        item $displaystyleint_1^x frac{e^t}{t},dt$, for $t>0$.
        end{itemize}
        end{exercise}

        Now we can print the exercises.

        printexercises

        end{document}


        enter image description here



        Be aware that with the approaches presented by now you cannot use printexercises for having exercises occur in arbitrary places. You can have exercises occur only in places of the document which in the source correspond to places behind the exercise-environments.



        Perhaps an environment which does read its content under verbatim-catcode-régime for unexpanded-writing it to .aux-file in a way where from the .aux-file it gets read back under verbatim-catcode-régime also for defining a macro where scantokens will be applied to, and thus some sort of re-implementation of the label-ref-mechanism or of the tableofcontents-mechanism for verbatimized stuff might make it possible to make exercises printable throughout the entire document.



        Implementing such a mechanism might be a nice challenge. But before taking that into consideration at all, exact information is needed on the intended usage and the desired "user-interface", i.e., what additional things you wish to be able to specify in which ways, etc, ...







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Mar 19 at 17:01









        Ulrich DiezUlrich Diez

        5,495620




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