Cfrgtkky

I want to create an environment, that generates a new command. There are some similar examples on google, but nothing fits exactly.

The minimal (not) working example shows best, what I want:

documentclass[12pt,a4paper]{article}

usepackage[utf8]{inputenc}



setlength{parindent}{0pt}



%Thats my environment:

newenvironment{LHZZ}[1]{

newcommand{csname LH#1endcsname }[1]bgroup

}{egroup}



%Thats the use of it. It is very important, that I can use arguments:  

begin{LHZZ}{XY}

write stuff here 



refer to #1

end{LHZZ}

The environment above should (but doesnt) equal the following:

% not part of the code !!!!!

newcommand{LHXY}[1]{

write stuff here



refer to #1

}

The following is the call in the document.

begin{document}

LHXY{parameter} %the command LHXY has been created indirectly by begin{LHZZ}

end{document}

The output should be:

write stuff here

refer to parameter

It doesnt work. It says csname is already defined. But I dont want to define csname. It is just the first command inside the argument. What do I have to change, to make this work?

Edit: There is a purpose for this, what seems to be code golfing. This should lead into a package which can be used by people who are not Tex-safe. The package is for making brochures for marriages, church service, etc. easily.

Edit 2:
I sticked to one of the given solutions as far as possible and far as I understood it. Unfortunately, I need one optional parameter. To understand, what is the meaning of this quirky code, have a look at the example songbook and the call of it. The almost final version as a still not working MWE:

%Business as usual

documentclass[12pt,a4paper]{book}

usepackage[utf8]{inputenc}

usepackage[german]{babel}

usepackage{environ}



%This sets a default value

newcommand{LHliederStandard}{n}



%This calls the environment(s)

newcommand{LHsong}[3][LHliederStandard]{

csname LH#2endcsname[#1]#3 %indirect call of what is defined in Liederbuch environment

}



makeatletter

%This is the Liederbuch environment (Liederbuch = songbook)

NewEnviron{Liederbuch}[1]{

xdefLB@my@temp{

noexpandnewcommand{csname LH#1endcsname}[2][relax]{

unexpandedexpandafter{BODY}

}

}

aftergroupLB@my@temp

}

makeatother



%This is the Lied environment (Lied = song)

NewEnviron{Lied}[2]{

ifnumnumexpr#2=numexpr##3 %the double # refers to parameter of the level above, or doesnt it.

ifnumpdfstrcmp{#1}{##2}=0

BODY

fi

fi

}



%example for a songbook

begin{Liederbuch}{songbook}



begin{Lied}{n}{1}

song 1 mode n

end{Lied}



begin{Lied}{nt}{2}

song 2 mode nt

end{Lied}



end{Liederbuch}



%call of the songbook

begin{document}



LHsong{songbook}{1}     %calls song 1 mode n

LHsong[nt]{songbook}{2} %calls song 2 mode nt

%hypothetical other songbook

LHsong[n]{childrensongs}{35}



end{document}

The command form is easier:

documentclass{article}



newcommand{LHZZ}[2]{%

  expandafternewcommandcsname LH#1endcsname[1]{#2}}%

}



begin{document}



LHZZ{XY}{%

  write stuff here



  refer to #1%

}



LHXY{parameter}



end{document}

If you really insist in using an environment, use environ:

documentclass{article}

usepackage{environ}



makeatletter

NewEnviron{LHZZ}[1]{%

  edefmaestroglanz@temp{%

    unexpanded{expandaftergdefcsname LH#1endcsname}####1{unexpandedexpandafter{BODY}}%

  }%

  maestroglanz@temp

}

makeatother



begin{document}



begin{LHZZ}{XY}

write stuff here



refer to #1

end{LHZZ}



LHXY{parameter}



end{document}

An implementation using xparse and expl3; the largest part of the code is the definition of the error messages in case the environment is called twice with the same argument.

documentclass{article}

usepackage{environ,xparse}



ExplSyntaxOn

NewEnviron{LHZZ}[1]

 {

  cs_set_protected:cV { LH#1:n } BODY

  cs_if_free:cTF { LH#1 }

   {

    cs_gset_eq:cc { LH#1 }{ LH#1:n }

   }

   {

    msg_error:nnn { maestroglanz/LH } { already-defined } { #1 }

   }

 }

cs_generate_variant:Nn cs_set_protected:Nn { cV }

msg_new:nnnn { maestroglanz/LH } { already-defined }

 {

  LH#1~already~defined

 }

 {

  You~used~token_to_str:N begin{LHZZ}{#1}~before

 }

ExplSyntaxOff



begin{document}



begin{LHZZ}{XY}

write stuff here 



refer to #1

end{LHZZ}



LHXY{parameter}



begin{LHZZ}{XY}aend{LHZZ}



end{document}

Without the error check, the code part would look like

ExplSyntaxOn

NewEnviron{LHZZ}[1]

 {

  cs_set_protected:cV { LH#1:n } BODY

  cs_gset_eq:cc { LH#1 }{ LH#1:n }

 }

cs_generate_variant:Nn cs_set_protected:Nn { cV }

ExplSyntaxOff

Update

With xparse released 2019-05-03 the code can become

documentclass{article}

usepackage{xparse}



ExplSyntaxOn

NewDocumentEnvironment{LHZZ}{m +b}

 {

  cs_set_protected:cn { LH#1:n } { #2 }

  cs_if_free:cTF { LH#1 }

   {

    cs_gset_eq:cc { LH#1 }{ LH#1:n }

   }

   {

    msg_error:nnn { maestroglanz/LH } { already-defined } { #1 }

   }

 }{}

msg_new:nnnn { maestroglanz/LH } { already-defined }

 {

  LH#1~already~defined

 }

 {

  You~used~token_to_str:N begin{LHZZ}{#1}~before

 }

ExplSyntaxOff



begin{document}



begin{LHZZ}{XY}

write stuff here 



refer to #1

end{LHZZ}



LHXY{parameter}



begin{LHZZ}{XY}aend{LHZZ}



end{document}

Here is your minimal example turned into a working one:

documentclass[a4paper]{article}

usepackage[T1]{fontenc}

usepackage[ascii]{inputenc}

usepackage{environ}



makeatletter



@ifdefinable@my@temporary{} % check availability of the name

% That's my environment:

NewEnviron{LHZZ}[1]{%

    let newcommand relax

    protected@xdef@my@temporary{%

        newcommand{csname LH#1endcsname}[1]{BODY}}%

    aftergroup@my@temporary

}



makeatother







begin{document}



% That's the use of it:  

begin{LHZZ}{XY}

    write stuff here 



    refer to ##1 % sorry, doubling "#" is necessary here

end{LHZZ}



LHXY{parameter} %the command LHXY has been created indirectly by begin{LHZZ}



end{document}

Edit: I think using newcommand instead of globaledef (see Christian’s answer; note, however, that globaledef is exactly the same as xdef) does have some added value, because one retains, for example, the ability to define a default argument:

documentclass[a4paper]{article}

usepackage[T1]{fontenc}

usepackage[ascii]{inputenc}

usepackage{environ}



makeatletter



@ifdefinable@my@temporary@x{} % check availability of the names

@ifdefinable@my@temporary@y{}

% That's my environment:

NewEnviron{LHZZ}[1]{%

    let newcommand relax

    protected@xdef@my@temporary@x{%

        newcommand{csname LH#1endcsname}[1]{BODY}

    }%

    % ... but this one works too (the astersik is there only to illustrate 

    % another possibility: define a non-"long" command):

    protected@xdef@my@temporary@y{%

        newcommand*{csname MG#1endcsname}[1][default]{BODY}

    }%

    aftergroup@my@temporary@x

    aftergroup@my@temporary@y

}



makeatother







begin{document}



% That's the use of it:  

begin{LHZZ}{XY}

    write stuff here 

    refer to ##1par % sorry, doubling "#" is necessary here

end{LHZZ}



Text before.



LHXY{parameter} %the command LHXY has been created indirectly by begin{LHZZ}

MGXY[parameter]

MGXY



Text after.



end{document}

Edit 2: Always double-check that the brain is connected before writing to TeX.SX! (Will it be, now?) Here is a cleaner implementation of the same basic idea:

documentclass[a4paper]{article}

usepackage[T1]{fontenc}

usepackage[ascii]{inputenc}

usepackage{environ}



makeatletter



@ifdefinable@my@temporary@x{} % check availability of the names

@ifdefinable@my@temporary@y{}

% That's my environment:

NewEnviron{LHZZ}[1]{%

    xdef@my@temporary@x{%

        noexpandnewcommand{csname LH#1endcsname}[1]{%

            unexpandedexpandafter{BODY}%

        }%

    }%

    % ... but this one works too (the astersik is there only to illustrate 

    % another possibility: define a non-"long" command):

    xdef@my@temporary@y{%

        noexpandnewcommand*{csname MG#1endcsname}[1][default]{%

            unexpandedexpandafter{BODY}%

        }%

    }%

    aftergroup@my@temporary@x

    aftergroup@my@temporary@y

    % Obviously, in a real application you'd choose only one of the two 

    % possibiities.

}



makeatother







begin{document}



begingroup % to show that normal scoping is obeyed



% That's the use of it:  

begin{LHZZ}{XY}

    write stuff here 

    refer to texttt{#1}par % doubling the "#" is no longer necessary

end{LHZZ}



Now verb|LHXY| is

begin{flushleft}

    ttfamily meaningLHXY

end{flushleft}



Text before.



LHXY{parameter} %the command LHXY has been created indirectly by begin{LHZZ}

MGXY[parameter]

MGXY



Text after.



endgroup



Here verb|LHXY| is textbf{%

    ifdefined LHXY definedelse not definedfi

}.



end{document}

But I’d better follow @egreg’s solicitation… (see comments ;-)