Le 03/03/2014 18:49, FNH nous fit lire :
> I know what ifdef does (the example below shows me using it)...
> 
> //#declare text2use = 2;
> 
> box     {
>         <-10,0,11>,<10,10,10>
> 
>         #ifdef(text2use)
>                 texture { pigment { White } }
>         #else
>                 texture { pigment { Green } }
>         #end
> 
>         }
> 
> .... but I'm struggling to understand when you would use it. Why would you refer
> to a variable you've not defined?  Isn't that just sloppy coding.
> 
> Has anyone got/had a real-use case for this command? I'd love to know what I'm
> missing out on.
> 
> 

you can define variable in code, but also in command line.

the most traditional use is the classical protection of include file: if
the value already exist, skip the definition.

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