[gambit-list] Hashing of types

Marc Feeley feeley at iro.umontreal.ca
Mon Aug 10 15:59:58 EDT 2009


On 10-Aug-09, at 3:31 PM, Alex Queiroz wrote:

> Hallo,
>
>     Is there a way to tell the table hashing function to ignore a
> field of a define-type'd value? I am writing a function for alpha-beta
> searching, and I'd like to use a cache to avoid re-searching
> previously calculated positions. So I have defined the type:
>
> (define-type node
>  id: d7aba792-963c-41c9-b1fd-e5e26590ab34
>
>  seq
>  ply
>  move
>  value                  ; cached value of evaluation function,
>                         ; not full search value
>  (board unprintable:))
>
> I need that the field 'move' be ignored by the hash function for
> equal?. Is that possible?

Use:

(define-type node
  id: d7aba792-963c-41c9-b1fd-e5e26590ab34

  seq
  ply
  move
  value                  ; cached value of evaluation function,
                         ; not full search value
  (board unprintable: equality-skip:))

Marc




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