Bug? LaTeX misparses nested optional arguments












16















LaTeX seems to be having problems handling nested optional arguments. I've included a minimal code example that generates the error:



documentclass[12pt,oneside]{book}

begin{document}



newcommand{termbad}[2]{#2#1}

newcommand{termgood}[2]{#2#1}



newcommand{up}[1]{#1}

newcommand{dd}[1]{#1}



termgood{up{Tart}}{Pop}

termbad[up{Tart}]{Pop}    



termgood{dd[Tart]}{Pop}

termbad[{dd[Tart]}]{Pop}

%termbad[dd[Tart]]{Pop}





end{document}


If you run this code, it works. If you remove the % in the second to last line, it fails with:



Runaway argument?



Tart{Pop} par par end {document}



!File ended while scanning use of dd.


After further tinkering, I have discovered the problem: LaTeX is reading the ] for the inner optional argument as the end of the outer optional argument and then passing a malformed argument in. So it is passing in dd[Tart as the optional argument to termbad instead of dd[Tart].



This still feels like a bug to me. Nesting braces in arguments works, brackets should as well. The following are workarounds:




  • Enclose the inner optional argument in braces (as in the line before %).


  • Redefine your inner function to require its argument instead of using optional arguments.


  • Redefine your outer function to require its argument instead of using optional arguments.



Any one of the three works around the issue.



(Reposted here; question was originally posted to stackexchange and then closed instead of being migrated.)






nesting optional-arguments







share|improve this question

























  • As far as I can see, the main problem is that LaTeX doesn't define the notion of nested optional arguments. This is why different implementations have different semantics.

    – user10274
    Oct 20 '12 at 11:57
















16















LaTeX seems to be having problems handling nested optional arguments. I've included a minimal code example that generates the error:



documentclass[12pt,oneside]{book}

begin{document}



newcommand{termbad}[2]{#2#1}

newcommand{termgood}[2]{#2#1}



newcommand{up}[1]{#1}

newcommand{dd}[1]{#1}



termgood{up{Tart}}{Pop}

termbad[up{Tart}]{Pop}    



termgood{dd[Tart]}{Pop}

termbad[{dd[Tart]}]{Pop}

%termbad[dd[Tart]]{Pop}





end{document}


If you run this code, it works. If you remove the % in the second to last line, it fails with:



Runaway argument?



Tart{Pop} par par end {document}



!File ended while scanning use of dd.


After further tinkering, I have discovered the problem: LaTeX is reading the ] for the inner optional argument as the end of the outer optional argument and then passing a malformed argument in. So it is passing in dd[Tart as the optional argument to termbad instead of dd[Tart].



This still feels like a bug to me. Nesting braces in arguments works, brackets should as well. The following are workarounds:




  • Enclose the inner optional argument in braces (as in the line before %).


  • Redefine your inner function to require its argument instead of using optional arguments.


  • Redefine your outer function to require its argument instead of using optional arguments.



Any one of the three works around the issue.



(Reposted here; question was originally posted to stackexchange and then closed instead of being migrated.)






nesting optional-arguments







share|improve this question

























  • As far as I can see, the main problem is that LaTeX doesn't define the notion of nested optional arguments. This is why different implementations have different semantics.

    – user10274
    Oct 20 '12 at 11:57














16












16








16


1






LaTeX seems to be having problems handling nested optional arguments. I've included a minimal code example that generates the error:



documentclass[12pt,oneside]{book}

begin{document}



newcommand{termbad}[2]{#2#1}

newcommand{termgood}[2]{#2#1}



newcommand{up}[1]{#1}

newcommand{dd}[1]{#1}



termgood{up{Tart}}{Pop}

termbad[up{Tart}]{Pop}    



termgood{dd[Tart]}{Pop}

termbad[{dd[Tart]}]{Pop}

%termbad[dd[Tart]]{Pop}





end{document}


If you run this code, it works. If you remove the % in the second to last line, it fails with:



Runaway argument?



Tart{Pop} par par end {document}



!File ended while scanning use of dd.


After further tinkering, I have discovered the problem: LaTeX is reading the ] for the inner optional argument as the end of the outer optional argument and then passing a malformed argument in. So it is passing in dd[Tart as the optional argument to termbad instead of dd[Tart].



This still feels like a bug to me. Nesting braces in arguments works, brackets should as well. The following are workarounds:




  • Enclose the inner optional argument in braces (as in the line before %).


  • Redefine your inner function to require its argument instead of using optional arguments.


  • Redefine your outer function to require its argument instead of using optional arguments.



Any one of the three works around the issue.



(Reposted here; question was originally posted to stackexchange and then closed instead of being migrated.)






nesting optional-arguments







share|improve this question
















LaTeX seems to be having problems handling nested optional arguments. I've included a minimal code example that generates the error:



documentclass[12pt,oneside]{book}

begin{document}



newcommand{termbad}[2]{#2#1}

newcommand{termgood}[2]{#2#1}



newcommand{up}[1]{#1}

newcommand{dd}[1]{#1}



termgood{up{Tart}}{Pop}

termbad[up{Tart}]{Pop}    



termgood{dd[Tart]}{Pop}

termbad[{dd[Tart]}]{Pop}

%termbad[dd[Tart]]{Pop}





end{document}


If you run this code, it works. If you remove the % in the second to last line, it fails with:



Runaway argument?



Tart{Pop} par par end {document}



!File ended while scanning use of dd.


After further tinkering, I have discovered the problem: LaTeX is reading the ] for the inner optional argument as the end of the outer optional argument and then passing a malformed argument in. So it is passing in dd[Tart as the optional argument to termbad instead of dd[Tart].



This still feels like a bug to me. Nesting braces in arguments works, brackets should as well. The following are workarounds:




  • Enclose the inner optional argument in braces (as in the line before %).


  • Redefine your inner function to require its argument instead of using optional arguments.


  • Redefine your outer function to require its argument instead of using optional arguments.



Any one of the three works around the issue.



(Reposted here; question was originally posted to stackexchange and then closed instead of being migrated.)






nesting optional-arguments




nesting optional-arguments






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Oct 20 '12 at 12:35









Kurt

36.4k847162




36.4k847162










asked Oct 20 '12 at 11:07









JKreftJKreft

260211




260211













  • As far as I can see, the main problem is that LaTeX doesn't define the notion of nested optional arguments. This is why different implementations have different semantics.

    – user10274
    Oct 20 '12 at 11:57



















  • As far as I can see, the main problem is that LaTeX doesn't define the notion of nested optional arguments. This is why different implementations have different semantics.

    – user10274
    Oct 20 '12 at 11:57

















As far as I can see, the main problem is that LaTeX doesn't define the notion of nested optional arguments. This is why different implementations have different semantics.

– user10274
Oct 20 '12 at 11:57





As far as I can see, the main problem is that LaTeX doesn't define the notion of nested optional arguments. This is why different implementations have different semantics.

– user10274
Oct 20 '12 at 11:57










1 Answer
1






active

oldest

votes


















23














When TeX reads arguments, then TeX only checks for matching curly braces (characters with catcode 1 and 2). Square brackets are not special in this sense. The first ] that is not hidden inside curly braces is taken as the end of the optional argument. Therefore an additional set of braces is the usual solution:



foo[{bar[...]}]{...}


It is only a bug, if this does not work, e.g. if the definition passes optional arguments to other commands:



deffoo#1#2{bar[#1]{#2}}


This should be



deffoo#1#2{bar[{#1}]{#2}}


Then #1 may contain square brackets, especially ].






share|improve this answer



















  • 7





    Worth noting that xparse-defined functions do not suffer from this

    – Joseph Wright♦
    Oct 20 '12 at 11:41











  • Thanks for the answers. I'm looking at xparse now, since I'm using some complex code to create a highly linked and formatted document. This may solve a few of the problems I've been having.

    – JKreft
    Oct 23 '12 at 12:33






  • 2





    an answer explicitly showing how xparse is used has been posted at How do I nest a command with an optional argument?

    – barbara beeton
    Apr 15 '16 at 15:55











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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









23














When TeX reads arguments, then TeX only checks for matching curly braces (characters with catcode 1 and 2). Square brackets are not special in this sense. The first ] that is not hidden inside curly braces is taken as the end of the optional argument. Therefore an additional set of braces is the usual solution:



foo[{bar[...]}]{...}


It is only a bug, if this does not work, e.g. if the definition passes optional arguments to other commands:



deffoo#1#2{bar[#1]{#2}}


This should be



deffoo#1#2{bar[{#1}]{#2}}


Then #1 may contain square brackets, especially ].






share|improve this answer



















  • 7





    Worth noting that xparse-defined functions do not suffer from this

    – Joseph Wright♦
    Oct 20 '12 at 11:41











  • Thanks for the answers. I'm looking at xparse now, since I'm using some complex code to create a highly linked and formatted document. This may solve a few of the problems I've been having.

    – JKreft
    Oct 23 '12 at 12:33






  • 2





    an answer explicitly showing how xparse is used has been posted at How do I nest a command with an optional argument?

    – barbara beeton
    Apr 15 '16 at 15:55
















23














When TeX reads arguments, then TeX only checks for matching curly braces (characters with catcode 1 and 2). Square brackets are not special in this sense. The first ] that is not hidden inside curly braces is taken as the end of the optional argument. Therefore an additional set of braces is the usual solution:



foo[{bar[...]}]{...}


It is only a bug, if this does not work, e.g. if the definition passes optional arguments to other commands:



deffoo#1#2{bar[#1]{#2}}


This should be



deffoo#1#2{bar[{#1}]{#2}}


Then #1 may contain square brackets, especially ].






share|improve this answer



















  • 7





    Worth noting that xparse-defined functions do not suffer from this

    – Joseph Wright♦
    Oct 20 '12 at 11:41











  • Thanks for the answers. I'm looking at xparse now, since I'm using some complex code to create a highly linked and formatted document. This may solve a few of the problems I've been having.

    – JKreft
    Oct 23 '12 at 12:33






  • 2





    an answer explicitly showing how xparse is used has been posted at How do I nest a command with an optional argument?

    – barbara beeton
    Apr 15 '16 at 15:55














23












23








23







When TeX reads arguments, then TeX only checks for matching curly braces (characters with catcode 1 and 2). Square brackets are not special in this sense. The first ] that is not hidden inside curly braces is taken as the end of the optional argument. Therefore an additional set of braces is the usual solution:



foo[{bar[...]}]{...}


It is only a bug, if this does not work, e.g. if the definition passes optional arguments to other commands:



deffoo#1#2{bar[#1]{#2}}


This should be



deffoo#1#2{bar[{#1}]{#2}}


Then #1 may contain square brackets, especially ].






share|improve this answer













When TeX reads arguments, then TeX only checks for matching curly braces (characters with catcode 1 and 2). Square brackets are not special in this sense. The first ] that is not hidden inside curly braces is taken as the end of the optional argument. Therefore an additional set of braces is the usual solution:



foo[{bar[...]}]{...}


It is only a bug, if this does not work, e.g. if the definition passes optional arguments to other commands:



deffoo#1#2{bar[#1]{#2}}


This should be



deffoo#1#2{bar[{#1}]{#2}}


Then #1 may contain square brackets, especially ].







share|improve this answer












share|improve this answer



share|improve this answer










answered Oct 20 '12 at 11:25









Heiko OberdiekHeiko Oberdiek

229k17555906




229k17555906








  • 7





    Worth noting that xparse-defined functions do not suffer from this

    – Joseph Wright♦
    Oct 20 '12 at 11:41











  • Thanks for the answers. I'm looking at xparse now, since I'm using some complex code to create a highly linked and formatted document. This may solve a few of the problems I've been having.

    – JKreft
    Oct 23 '12 at 12:33






  • 2





    an answer explicitly showing how xparse is used has been posted at How do I nest a command with an optional argument?

    – barbara beeton
    Apr 15 '16 at 15:55














  • 7





    Worth noting that xparse-defined functions do not suffer from this

    – Joseph Wright♦
    Oct 20 '12 at 11:41











  • Thanks for the answers. I'm looking at xparse now, since I'm using some complex code to create a highly linked and formatted document. This may solve a few of the problems I've been having.

    – JKreft
    Oct 23 '12 at 12:33






  • 2





    an answer explicitly showing how xparse is used has been posted at How do I nest a command with an optional argument?

    – barbara beeton
    Apr 15 '16 at 15:55








7




7





Worth noting that xparse-defined functions do not suffer from this

– Joseph Wright♦
Oct 20 '12 at 11:41





Worth noting that xparse-defined functions do not suffer from this

– Joseph Wright♦
Oct 20 '12 at 11:41













Thanks for the answers. I'm looking at xparse now, since I'm using some complex code to create a highly linked and formatted document. This may solve a few of the problems I've been having.

– JKreft
Oct 23 '12 at 12:33





Thanks for the answers. I'm looking at xparse now, since I'm using some complex code to create a highly linked and formatted document. This may solve a few of the problems I've been having.

– JKreft
Oct 23 '12 at 12:33




2




2





an answer explicitly showing how xparse is used has been posted at How do I nest a command with an optional argument?

– barbara beeton
Apr 15 '16 at 15:55





an answer explicitly showing how xparse is used has been posted at How do I nest a command with an optional argument?

– barbara beeton
Apr 15 '16 at 15:55


















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