Re: Multiple keys for a map

[Shark8 <onewingedshark@gmail.com>]

On Tuesday, September 17, 2013 8:51:24 AM UTC-6, Peter Brooks wrote:
> I know that maps in Containers.Hashed_Maps and Containers.Ordered_Map are designed as single-key look-up tables.
> 
> Is there an extension that allows multiple keys? 
> 
> I'd like to be able to do something like this:
> 
> procedure Insert (Container : in out Map;
>                   key1, key2, key3       : in     Key_Type;
>                   New_Item  : in     Element_Type;
>                   Position  :    out Cursor;
>                   Inserted  :    out Boolean);
> 
> allowing:
> 
> insert(my_map,"fox","jumps","dog","The quick brown fox jumps over the lazy dog",location,succeeded);
> insert(my_map,"cow","jumps","moon","The cow jumps over the moon",location,succeeded);
> insert(my_map,"dog","jumps","log","The lazy dog jumps over the small log",location,succeeded);
> insert(my_map,"dog","jumps","bed","The very lazy dog jumps into bed",location,succeeded)
> 
> So that later, I can have:
> Subject := find(my_map,"fox",-,-);
> Verb := find(my_map,-,"jumps",-);
> Object := find(my_map,-,-,"dog");
> 
> and, after this:
> Subject = Verb = Object;
> 
> I know this could be done with three calls to Insert, but I also want to be able to call:
> 
> find(mymap,"fox","jumps","dog") => true
> and
> find(mymap,"dog","jumps","fox") => false
> and, ideally,
> find(myman,"dog",-,-) => 
> 
> "The Lazy dog jumps over the small log"
> "The very lazy dog jumps into bed"
> 
> Any suggestions?

I'm vaguely reminded of Prolog by this question: this problem was basically the intro for the book I had.