Re: [bug #15690] Refactor /MISSING subcommands.

[John Darrington]

On Wed, Sep 27, 2006 at 07:48:25AM -0700, Benjamin Levy Pfaff wrote:
     
     OK.  Then let's create a new abstract data type, a "case_filter" or some
     such.  To get a casereader with a filter, you pass one in, otherwise you
     pass in a null pointer, so there's only a single additional argument. 
     Cloned casereaders keep the same filter.  When no casereader or clone is
     still using a filter, it gets destroyed; either reference counting or
     case_filter cloning could be used.

I've been looking at this again.  I don't think it will be necessary
to abstract the case_filter.  A simple object containing an array of
variables, and a bool to indicate whether user missing values should
be excluded will, I think, be sufficient for all scenarios I can
foresee.  If more complicated situations arise, then we can generalise
a little, or abstract the type if and when that becomes necessary.   

I think a simple reference counted struct passed to
casefile_get_reader will do the job, and be least troublesome to use.

J'
     
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