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Excerpts from Lee, Alexis's message of 2014-11-05 15:46:43 +0100:
> I'm considering adding a function which takes a list and returns the first
> non-null, non-empty value in that list.
> 
> So you could do EG:
> 
>     some_thing:
>         config:
>             ControlVIP:
>                 first_nonnull:
>                 - {get_param: ControlVIP}
>                 - {get_attr: [ControlVirtualIP, fixed_ips, 0, ip_address]}]}
> 
> I'm open to other names, EG "some", "or", "fallback_list" etc.
> 
> Steve Hardy suggested building this into get_attr or Fn::Select. My feeling
> is that those each do one job well right now, I'm happy to take a steer
> though.
> 
> What do you think please?
> 

Yes this is super useful for writing responsive, reusable templates.

I'd like to suggest that this be called 'coalesce' as that is what SQL
calls it.