Hcfyk

So I am thinking of creating a macro that takes any latex code as an argument. For example,

newcommandpurp[1]{color{purple} #1}

I hoped that this macro would make any latex code inside of purp to be colored as purple. I realized, however, is that if I pass some environment (begin.. end) to the argument, some weird latex error occurs. For example.

purp{

begin{verbatim} 

asdfadf

asdf

asdf

end{verbatim}

}

breaks the verbatim output and generates bunch of latex errors. Is there any safe way to make a function that takes arbitrary latex code as an argument?

Edit

Besides a verbatim, I also observed that following produces very weird error.

purp{

    [

 x= begin{cases*}

  y & if x_1 text{ is } 1\

  z & if x_2 text{ is }  2

end{cases*} 

]

}

This gives a weird error Missing $ is inserted. Any idea why?

The near universal rule is that verbatim material cannot be an argument to a command. With the cprotect package, there is sometimes a workaround as shown in the MWE, but even that is not a universal fix.

EDIT: group added to prevent spillage of purple into subsequent material (thanks Ulrike).

documentclass{article}

usepackage{cprotect,xcolor}

newcommandpurp[1]{{color{purple} #1}}

begin{document}

cprotectpurp{

begin{verbatim} 

asdfadf

asdf

asdf

end{verbatim}

}

end{document}

If it's just about colours, you could fake a textcolor command, which seems to take an argument, but does support verbatim material. Note that this is no general solution, but just provides an argument taking syntax to color which is not really an argument.

(This way one could use any formatting switches not only colours, e.g. bfseries could be used this way, too)

EDIT: created a switchhack that allows arbitrary formatting switches not only colours, and colorhack calls switchhack now.

documentclass{article}



usepackage{xcolor}



makeatletter

begingroupdef:#1{endgroupletswitchhack@sptoken= #1}:{ }

newcommandswitchhack[1]

  {%

    defswitchhack@switch{#1}%

    switchhack@a

  }

newcommandswitchhack@a

  {%

    futureletswitchhack@gobbledswitchhack@b

  }

newcommandswitchhack@b

  {%

    ifxswitchhack@gobbledswitchhack@sptoken

      switchhack@eatspace

    fi

    @firstofone

    {%

      ifxbgroupswitchhack@gobbled

      else

        GenericWarning

          {}{Warning: Argument of stringswitchhackspace not delimited}%

        switchhack@undelimeted

      fi

      switchhack@delimited

    }%

  }

longdefswitchhack@eatspacefi#1#2%

  {%

    fi

    afterassignmentswitchhack@a

    letswitchhack@gobbled=

  }

longdefswitchhack@undelimetedfi#1#2%

  {%

    fi

    {switchhack@switch#2}%

  }

newcommandswitchhack@delimited

  {%

    afterassignmentswitchhack@do

    letswitchhack@gobbled

  }

newcommandswitchhack@do

  {%

    bgroupswitchhack@switch

  }

longdefcolorhack#1#{colorhack@{#1}}

newcommandcolorhack@[2]

  {%

    switchhack{color#1{#2}}%

  }

makeatother



newcommandpurp{colorhack{purple}}

newcommandbfhack{switchhack{bfseries}}



begin{document}

colorhack[rgb]{.5 .4 .8}{foo}

purp{verb|this is blue|}

following text

bfhack{this is bold}



colorhack{red} Undelimeted



purp{

  begin{verbatim}

  This is

  verbatim

  purple (I lied up there, it never was blue)

  end{verbatim}

}

end{document}

Another possibility to get macros which take verbatim material as arguments is to grab the arguments as boxes instead. Again this is no universal solution and you can't do arbitrary stuff with it (most importantly you can't change the appearance of the boxed material after it is boxed, that's what the optional arguments of grabbox are for, to make some formatting possible).

The following defines purp to take its argument inside of a hbox and purp* to take it inside of a vbox (of course the macro name in both cases is purp, the second one is just followed by a star).

documentclass{article}



usepackage{grabbox}

usepackage{xcolor}



makeatletter

newsaveboxpurp@box

newcommandpurp

  {%

    begingroup

    @ifstar

      {%

        grabboxpurp@box[color{purple}]vbox{unvboxpurp@boxendgroup}%

      }

      {%

        grabboxpurp@box[color{purple}]hbox{unhboxpurp@boxendgroup}%

      }%

  }

makeatother



begin{document}

purp{verb|this is blue|}



other text



purp*{

  begin{verbatim}

  This is

  verbatim

  purple (I lied up there, it never was blue)

  end{verbatim}

}

end{document}