Mr. Art wrote in message <392### [at] gcinet>...
>If #ifndef() could return false for constants or if there could
>be a value that #ifndef could test properly, we could make
>scene files that could adjust to the allowed features and the
>end user need not _have_ to know which files need special
>attention, or have to choose which flavor POV to use.


#ifdef(unofficial_version) should return false in the official version of
POV-Ray.  In MegaPOV, it is always defined, but will be -1 if unofficial
features are disabled.  This allows the following code to be used to decide
if unofficial features are available:

#ifdef(unofficial_version)
  #if(unofficial_version = -1)
    Official = true;
  #else
    Official = false;
  #end
#else
  Official = true;
#end

You can then use the value of Official elsewhere in your scene file to
determine if unofficial features can be used or not.  This, however, says
nothing about which unofficial features can be used.

Mark

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