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How do you write a macro that takes arguments containing paragraphs?

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2

I'm trying to write a macro that takes arguments containing paragraphs. If you write a normal macro and one of its arguments contains a paragraph, it will break:

documentclass{article}

usepackage[utf8]{inputenc}



title{test}



begin{document}



maketitle



section{Introduction}



defmymacro#1{#1}



mymacro{This



contains a paragraph}



end{document}

This produces an error:

Runaway argument?

{This

! Paragraph ended before mymacro was complete.

<to be read again> 

                   par

l.15

So I tried to redefine par for expanding the arguments of the macro, but now it won't stop compiling:

documentclass{article}

usepackage[utf8]{inputenc}



title{test}



begin{document}



maketitle



section{Introduction}



gdefoldpar{par}



defmymacro{gdefpar{}mymacroi}



defmymacroi#1{#1gdefpar{oldpar}}



mymacro{foo



bar}



end{document}

macros tex-core paragraphs arguments

share|improve this question

edited 3 hours ago

Phelype Oleinik

23.9k54587

asked 6 hours ago

sgfsgf

29517

• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  
  Use longdef or newcommand.
  
  – Phelype Oleinik
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  I recommend defining a new environment instead of a command.
  
  – JouleV
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @PhelypeOleinik If you make that an answer, I'll accept it. I was so sure that I had written commands in the past whose arguments could span paragraphs. It makes sense now, it was before I started using def instead of newcommnad.
  
  – sgf
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  def is not a latex command, newcommand which, is already allows paragraphs.
  
  – David Carlisle
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @DavidCarlisle Sometimes I need versions of def. I have no idea how to replicate edef, gdef or xdef with newcommand (which I believe is gdef?). What does it even mean for a tex command not to be a latex command?
  
  – sgf
  5 hours ago
  

  
  
  
  

 | 
show 2 more comments

2

I'm trying to write a macro that takes arguments containing paragraphs. If you write a normal macro and one of its arguments contains a paragraph, it will break:

documentclass{article}

usepackage[utf8]{inputenc}



title{test}



begin{document}



maketitle



section{Introduction}



defmymacro#1{#1}



mymacro{This



contains a paragraph}



end{document}

This produces an error:

Runaway argument?

{This

! Paragraph ended before mymacro was complete.

<to be read again> 

                   par

l.15

So I tried to redefine par for expanding the arguments of the macro, but now it won't stop compiling:

documentclass{article}

usepackage[utf8]{inputenc}



title{test}



begin{document}



maketitle



section{Introduction}



gdefoldpar{par}



defmymacro{gdefpar{}mymacroi}



defmymacroi#1{#1gdefpar{oldpar}}



mymacro{foo



bar}



end{document}

macros tex-core paragraphs arguments

share|improve this question

edited 3 hours ago

Phelype Oleinik

23.9k54587

asked 6 hours ago

sgfsgf

29517

• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  
  Use longdef or newcommand.
  
  – Phelype Oleinik
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  I recommend defining a new environment instead of a command.
  
  – JouleV
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @PhelypeOleinik If you make that an answer, I'll accept it. I was so sure that I had written commands in the past whose arguments could span paragraphs. It makes sense now, it was before I started using def instead of newcommnad.
  
  – sgf
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  def is not a latex command, newcommand which, is already allows paragraphs.
  
  – David Carlisle
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @DavidCarlisle Sometimes I need versions of def. I have no idea how to replicate edef, gdef or xdef with newcommand (which I believe is gdef?). What does it even mean for a tex command not to be a latex command?
  
  – sgf
  5 hours ago
  

  
  
  
  

 | 
show 2 more comments

I'm trying to write a macro that takes arguments containing paragraphs. If you write a normal macro and one of its arguments contains a paragraph, it will break:

documentclass{article}

usepackage[utf8]{inputenc}



title{test}



begin{document}



maketitle



section{Introduction}



defmymacro#1{#1}



mymacro{This



contains a paragraph}



end{document}

This produces an error:

Runaway argument?

{This

! Paragraph ended before mymacro was complete.

<to be read again> 

                   par

l.15

So I tried to redefine par for expanding the arguments of the macro, but now it won't stop compiling:

documentclass{article}

usepackage[utf8]{inputenc}



title{test}



begin{document}



maketitle



section{Introduction}



gdefoldpar{par}



defmymacro{gdefpar{}mymacroi}



defmymacroi#1{#1gdefpar{oldpar}}



mymacro{foo



bar}



end{document}

macros tex-core paragraphs arguments

share|improve this question

edited 3 hours ago

Phelype Oleinik

23.9k54587

asked 6 hours ago

sgfsgf

29517

documentclass{article}

usepackage[utf8]{inputenc}



title{test}



begin{document}



maketitle



section{Introduction}



defmymacro#1{#1}



mymacro{This



contains a paragraph}



end{document}

documentclass{article}

usepackage[utf8]{inputenc}



title{test}



begin{document}



maketitle



section{Introduction}



gdefoldpar{par}



defmymacro{gdefpar{}mymacroi}



defmymacroi#1{#1gdefpar{oldpar}}



mymacro{foo



bar}



end{document}

share|improve this question

edited 3 hours ago

Phelype Oleinik

23.9k54587

asked 6 hours ago

sgfsgf

29517

share|improve this question

edited 3 hours ago

Phelype Oleinik

23.9k54587

asked 6 hours ago

sgfsgf

29517

edited 3 hours ago

Phelype Oleinik

23.9k54587

edited 3 hours ago

Phelype Oleinik

23.9k54587

asked 6 hours ago

sgfsgf

29517

asked 6 hours ago

sgfsgf

29517

1 Answer
1

active

oldest

votes

8

At the time TeX was written, one page of a document would take several minutes to be processed, and syntax highlighting was not a thing, so it was a good thing to have some mechanism to detect if you forgot a }. A def, by default, doesn't allow a par token unless you explicitly say it's a longdef:

defmymacro#1{#1}

LaTeX, on the other hand, uses that by default, so if you use proper LaTeX commands (def shouldn't be used in LaTeX documents), newcommand makes a longdef by default. If you want a “short” def then you use newcommand*.

xparse returns the short argument default, but lets you define a long macro using the + argument modifier:

NewDocumentCommandmymacro{ m}{#1}% def

NewDocumentCommandmymacro{+m}{#1}% longdef

---

Your second attempt is clever, and it could have worked except for two things.

First is that you are using gdefoldpar{par} and then gdefpar{oldpar}. Once you expand par you get oldpar which, when expanded, yields par which, when expanded, yields oldpar which, when expanded, yields par which, when expanded, yields oldpar... Running forever :/

You need to use let (or globallet to have global effect) in this case: letoldparpar. This creates an exact copy of par named oldpar which does not depend on what is par.

Second, the runaway argument checking is implemented in a lower level, independent of the definition of par, so this would fail with the same error:

letparrelax

defmymacro#1{#1}

mymacro{foo



bar}

because when TeX sees two endlinechar tokens (which is a space by default) TeX inserts an implicit par token, which raises the Runaway argument error. Knowing that, then:

newcountoldELchar

oldELchar=endlinechar

defmymacro{endlinechar=-1relaxmymacroi}

defmymacroi#1{#1endlinechar=oldELchar}

mymacro{foo



bar}

won't raise an error, but a new line won't be a space anymore.

share|improve this answer

answered 5 hours ago

Phelype OleinikPhelype Oleinik

23.9k54587

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Haha, I was wondering where I went into infinite recursion...
  
  – sgf
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @sgf You can say, for instance, tracingall before the command you suspect is infinite-looping. You'll get a ton of garbage in the terminal and the log, but it gets easier to find out what is TeX doing.
  
  – Phelype Oleinik
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I would take a slight difference with the statement "(def shouldn't be used in LaTeX documents)". Certain service routines a user writes may require the special parsing provided by def syntax. I think it would be better to say "(def should be avoided, where possible)".
  
  – Steven B. Segletes
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  the endlinechar version has to be used with care, for example it also removes the end of line after mymacro (even if there is text following mymacro) not just the one in the argument.
  
  – David Carlisle
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  tex takes a line at a time and inserts the character specified by endlinechar at the point it grabs the next line at the end of the buffer before tokenizing., so its timing is well defined but er "delicate" :-)
  
  – David Carlisle
  5 hours ago
  

  
  
  
  

 | 
show 9 more comments

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8

At the time TeX was written, one page of a document would take several minutes to be processed, and syntax highlighting was not a thing, so it was a good thing to have some mechanism to detect if you forgot a }. A def, by default, doesn't allow a par token unless you explicitly say it's a longdef:

defmymacro#1{#1}

LaTeX, on the other hand, uses that by default, so if you use proper LaTeX commands (def shouldn't be used in LaTeX documents), newcommand makes a longdef by default. If you want a “short” def then you use newcommand*.

xparse returns the short argument default, but lets you define a long macro using the + argument modifier:

NewDocumentCommandmymacro{ m}{#1}% def

NewDocumentCommandmymacro{+m}{#1}% longdef

---

Your second attempt is clever, and it could have worked except for two things.

First is that you are using gdefoldpar{par} and then gdefpar{oldpar}. Once you expand par you get oldpar which, when expanded, yields par which, when expanded, yields oldpar which, when expanded, yields par which, when expanded, yields oldpar... Running forever :/

You need to use let (or globallet to have global effect) in this case: letoldparpar. This creates an exact copy of par named oldpar which does not depend on what is par.

Second, the runaway argument checking is implemented in a lower level, independent of the definition of par, so this would fail with the same error:

letparrelax

defmymacro#1{#1}

mymacro{foo



bar}

because when TeX sees two endlinechar tokens (which is a space by default) TeX inserts an implicit par token, which raises the Runaway argument error. Knowing that, then:

newcountoldELchar

oldELchar=endlinechar

defmymacro{endlinechar=-1relaxmymacroi}

defmymacroi#1{#1endlinechar=oldELchar}

mymacro{foo



bar}

won't raise an error, but a new line won't be a space anymore.

share|improve this answer

answered 5 hours ago

Phelype OleinikPhelype Oleinik

23.9k54587

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Haha, I was wondering where I went into infinite recursion...
  
  – sgf
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @sgf You can say, for instance, tracingall before the command you suspect is infinite-looping. You'll get a ton of garbage in the terminal and the log, but it gets easier to find out what is TeX doing.
  
  – Phelype Oleinik
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I would take a slight difference with the statement "(def shouldn't be used in LaTeX documents)". Certain service routines a user writes may require the special parsing provided by def syntax. I think it would be better to say "(def should be avoided, where possible)".
  
  – Steven B. Segletes
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  the endlinechar version has to be used with care, for example it also removes the end of line after mymacro (even if there is text following mymacro) not just the one in the argument.
  
  – David Carlisle
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  tex takes a line at a time and inserts the character specified by endlinechar at the point it grabs the next line at the end of the buffer before tokenizing., so its timing is well defined but er "delicate" :-)
  
  – David Carlisle
  5 hours ago
  

  
  
  
  

 | 
show 9 more comments

8

At the time TeX was written, one page of a document would take several minutes to be processed, and syntax highlighting was not a thing, so it was a good thing to have some mechanism to detect if you forgot a }. A def, by default, doesn't allow a par token unless you explicitly say it's a longdef:

defmymacro#1{#1}

LaTeX, on the other hand, uses that by default, so if you use proper LaTeX commands (def shouldn't be used in LaTeX documents), newcommand makes a longdef by default. If you want a “short” def then you use newcommand*.

xparse returns the short argument default, but lets you define a long macro using the + argument modifier:

NewDocumentCommandmymacro{ m}{#1}% def

NewDocumentCommandmymacro{+m}{#1}% longdef

---

Your second attempt is clever, and it could have worked except for two things.

First is that you are using gdefoldpar{par} and then gdefpar{oldpar}. Once you expand par you get oldpar which, when expanded, yields par which, when expanded, yields oldpar which, when expanded, yields par which, when expanded, yields oldpar... Running forever :/

You need to use let (or globallet to have global effect) in this case: letoldparpar. This creates an exact copy of par named oldpar which does not depend on what is par.

Second, the runaway argument checking is implemented in a lower level, independent of the definition of par, so this would fail with the same error:

letparrelax

defmymacro#1{#1}

mymacro{foo



bar}

because when TeX sees two endlinechar tokens (which is a space by default) TeX inserts an implicit par token, which raises the Runaway argument error. Knowing that, then:

newcountoldELchar

oldELchar=endlinechar

defmymacro{endlinechar=-1relaxmymacroi}

defmymacroi#1{#1endlinechar=oldELchar}

mymacro{foo



bar}

won't raise an error, but a new line won't be a space anymore.

share|improve this answer

answered 5 hours ago

Phelype OleinikPhelype Oleinik

23.9k54587

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Haha, I was wondering where I went into infinite recursion...
  
  – sgf
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @sgf You can say, for instance, tracingall before the command you suspect is infinite-looping. You'll get a ton of garbage in the terminal and the log, but it gets easier to find out what is TeX doing.
  
  – Phelype Oleinik
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I would take a slight difference with the statement "(def shouldn't be used in LaTeX documents)". Certain service routines a user writes may require the special parsing provided by def syntax. I think it would be better to say "(def should be avoided, where possible)".
  
  – Steven B. Segletes
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  the endlinechar version has to be used with care, for example it also removes the end of line after mymacro (even if there is text following mymacro) not just the one in the argument.
  
  – David Carlisle
  5 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  tex takes a line at a time and inserts the character specified by endlinechar at the point it grabs the next line at the end of the buffer before tokenizing., so its timing is well defined but er "delicate" :-)
  
  – David Carlisle
  5 hours ago
  

  
  
  
  

 | 
show 9 more comments

At the time TeX was written, one page of a document would take several minutes to be processed, and syntax highlighting was not a thing, so it was a good thing to have some mechanism to detect if you forgot a }. A def, by default, doesn't allow a par token unless you explicitly say it's a longdef:

defmymacro#1{#1}

LaTeX, on the other hand, uses that by default, so if you use proper LaTeX commands (def shouldn't be used in LaTeX documents), newcommand makes a longdef by default. If you want a “short” def then you use newcommand*.

xparse returns the short argument default, but lets you define a long macro using the + argument modifier:

NewDocumentCommandmymacro{ m}{#1}% def

NewDocumentCommandmymacro{+m}{#1}% longdef

---

Your second attempt is clever, and it could have worked except for two things.

First is that you are using gdefoldpar{par} and then gdefpar{oldpar}. Once you expand par you get oldpar which, when expanded, yields par which, when expanded, yields oldpar which, when expanded, yields par which, when expanded, yields oldpar... Running forever :/

You need to use let (or globallet to have global effect) in this case: letoldparpar. This creates an exact copy of par named oldpar which does not depend on what is par.

Second, the runaway argument checking is implemented in a lower level, independent of the definition of par, so this would fail with the same error:

letparrelax

defmymacro#1{#1}

mymacro{foo



bar}

because when TeX sees two endlinechar tokens (which is a space by default) TeX inserts an implicit par token, which raises the Runaway argument error. Knowing that, then:

newcountoldELchar

oldELchar=endlinechar

defmymacro{endlinechar=-1relaxmymacroi}

defmymacroi#1{#1endlinechar=oldELchar}

mymacro{foo



bar}

won't raise an error, but a new line won't be a space anymore.

share|improve this answer

answered 5 hours ago

Phelype OleinikPhelype Oleinik

23.9k54587

defmymacro#1{#1}

NewDocumentCommandmymacro{ m}{#1}% def

NewDocumentCommandmymacro{+m}{#1}% longdef

letparrelax

defmymacro#1{#1}

mymacro{foo



bar}

newcountoldELchar

oldELchar=endlinechar

defmymacro{endlinechar=-1relaxmymacroi}

defmymacroi#1{#1endlinechar=oldELchar}

mymacro{foo



bar}

share|improve this answer

answered 5 hours ago

Phelype OleinikPhelype Oleinik

23.9k54587

answered 5 hours ago

Phelype OleinikPhelype Oleinik

23.9k54587

answered 5 hours ago

Phelype OleinikPhelype Oleinik

23.9k54587