Kdtyjb

I'm attempting to create documents of a priori unknown length that is determined by a set of conditions. I'm generating LaTeX variables, including conditional variables, using Python. Within a variables LaTeX file, I have something resembling:

newcommand{VariableList}{VariableOne,VariableTwo}

newcommand{VariableOneSubOne}{SomeValueOne}

newcommand{VariableOneSubTwo}{SomeOtherValueOne}

newififVariableOneCondOne

VariableOneCondOnetrue

newcommand{VariableTwoSubOne}{SomeValueTwo}

newcommand{VariableTwoSubTwo}{SomeOtherValueTwo}

newififVariableTwoCondOne

VariableTwoCondOnefalse

Where the number of variables are not known. I loop over each variable and have some text that includes the values dynamically defined by the variables.

foreach n in VariableList{

Here is some text with inputnum{n}{SubOne} and inputnum{n}{SubTwo}.

}

Where I have defined:

newcommand{inputnum}[2]{expandaftercsname #1#2endcsname}

How can I define a similar command to take advantage of the conditional variables I have defined above? For example, I tried:

newcommand{inputcondnum}[2]{expandaftercsname if#1#2endcsname}

using the logic that the macro would replace

inputcondnum{n}{CondOne} 

with the following

ifVariableOneCondOne

but that does not seem to work. Any suggestions on how to use these dynamically generated conditional variables?

Here is a minimum example:

documentclass{article}

usepackage{pgffor}



% Command to generate variables

newcommand{inputnum}[2]{expandaftercsname #1#2endcsname}

newcommand{inputcondnum}[2]{expandaftercsname if#1#2endcsname}



% Variable definitions

newcommand{VariableList}{VariableOne,VariableTwo}

newcommand{VariableOneSubOne}{SomeValueOne}

newcommand{VariableOneSubTwo}{SomeOtherValueOne}

newififVariableOneCondOne

VariableOneCondOnetrue

newcommand{VariableTwoSubOne}{SomeValueTwo}

newcommand{VariableTwoSubTwo}{SomeOtherValueTwo}

newififVariableTwoCondOne

VariableTwoCondOnefalse





begin{document}



foreach n in VariableList{

Here is some text with inputnum{n}{SubOne} and inputnum{n}{SubTwo}. 



inputcondnum{n}{CondOne} Include this text if true else Include this text if false. fi

}

end{document} 

It's generally best to avoid the issue but you can make it work as

documentclass{article}

usepackage{pgffor}



% Command to generate variables

newcommand{inputnum}[2]{expandaftercsname #1#2endcsname}

newcommand{inputcondnum}[2]{expandaftercsname if#1#2endcsname}



% Variable definitions

newcommand{VariableList}{VariableOne,VariableTwo}

newcommand{VariableOneSubOne}{SomeValueOne}

newcommand{VariableOneSubTwo}{SomeOtherValueOne}

newififVariableOneCondOne

VariableOneCondOnetrue

newcommand{VariableTwoSubOne}{SomeValueTwo}

newcommand{VariableTwoSubTwo}{SomeOtherValueTwo}

newififVariableTwoCondOne

VariableTwoCondOnefalse





begin{document}



foreach n in VariableList{

Here is some text with inputnum{n}{SubOne} and inputnum{n}{SubTwo}. 



iftruecsname fiendcsnameinputcondnum{n}{CondOne} Include this text if true else Include this text if false. fi

}

end{document}

the issue is that TeX skips over if....fi constructs but it needs to see if... at the same time as it does not do expansion while skipping over "false" sections.

Note also that the expandafter are not needed in

newcommand{inputnum}[2]{expandaftercsname #1#2endcsname}

newcommand{inputcondnum}[2]{expandaftercsname if#1#2endcsname}

in the first case, because csname expands its content anyway so forcing expansion earlier with expandafter results in the same name being constructed. In the second case the expandafter does nothing at all as i is not expandable.

Resurrecting this old question to leave a somewhat cleaner solution, just for posterity.

If, for whatever reason, you're committed to the csname if...endcsname construct (say, if you need to pass the names of already-defined conditionals), a much cleaner solution than the iftruecsname fiendcsnameinputcondnum... hackery is to simply put the entire if...fi construct inside a macro.

The problem arises when your csname if...endcsname is nested inside another conditional—in this case, a hidden one controlling the foreach loop. To elaborate a little on David's answer, when executing a conditional, TeX does some bookkeeping to track of nested if...fis. If a conditional is false, it skips ahead to the next fi (or next else), but it needs to know which fi to skip to. When the skipped text contains a second if...fi, it takes note, and makes sure to continue past the inner fi and keep skipping ahead to the outer fi. However, it doesn't perform any expansions while it's looking for its fi. As a result, when the inner if... is hidden inside another macro (like csname...endcsname) but the fi is still in plain view, its bookkeeping gets thrown off, and everything goes haywire.

The solution is to make sure the if... and the matching fi are both tucked away inside a macro, making sure one is never seen without the other. In your case, you'd modify the minimal example to something like this (with a little formatting for readability):

documentclass{article}

setlength{parindent}{0pt}setlength{parskip}{10pt} %readability

usepackage{pgffor}



% Command to generate variables

newcommand{inputnum}[2]{csname #1#2endcsname}

newcommand{inputcondnum}[2]{csname if#1#2endcsname}



% Variable definitions

newcommand{VariableList}{VariableOne,VariableTwo}



newcommand{VariableOneSubOne}{SomeValueOne}

newcommand{VariableOneSubTwo}{SomeOtherValueOne}

newcommand{VariableTwoSubOne}{SomeValueTwo}

newcommand{VariableTwoSubTwo}{SomeOtherValueTwo}



newififVariableOneCondOne

newififVariableTwoCondOne

VariableOneCondOnetrue

VariableTwoCondOnefalse



%COMMAND TO TEST CONDITIONAL AND EXECUTE DESIRED CODE

newcommand{testcondnum}[4]{inputcondnum{#1}{#2} #3 else #4 fi}



begin{document}



%A simple implementation



{bfseries Simple}:



foreach n in VariableList{%

    texttt{textbackslash n} is n.\%

    Here is some text with inputnum{n}{SubOne} and inputnum{n}{SubTwo}. \%

    testcondnum{n}{CondOne}{Include this text if true.}{Include this text if false.}



}



%If you want vary what's going on inside the conditional,

%re-define a macro on each pass through the loop with the

% relevant code to execute. You'll probably want to define 

%it with def here, since def doesn't care about overwriting 

%old commands. With newcommand and renewcommand, you'd need

%to worry about using one on the first pass and the other 

%on subsequent passes.



%Of course, you could also just keep feeding the "Include 

%this..." bits straight into testcondnum, but for more 

%complicated code, using macros will probably be easier.



{bfseries Dynamic}:



foreach n in VariableList{    

    defdothisiftrue{Include this text if n CondOne is true.}

    defdothisiffalse{Include this text if n CondOne is false.}  

    texttt{textbackslash n} is n.\%

    Here is some text with inputnum{n}{SubOne} and inputnum{n}{SubTwo}. \%

    testcondnum{n}{CondOne}{dothisiftrue}{dothisiffalse}



}



end{document}

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