It certainly helped :)
I played around with it last night after chouser's response and it all made
sense, thanks!
Cheers,
Leonardo Borges
www.leonardoborges.com
On 15/09/2011, at 1:39 AM, Sean Corfield <seancorfi...@gmail.com> wrote:
> On Wed, Sep 14, 2011 at 5:58 AM, Leonardo Borges
> <leonardoborges...@gmail.com> wrote:
>> (defn neighbors
>> ([size yx] (neighbors [[-1 0] [1 0] [0 -1] [0 1]] size yx))
>> ([deltas size yx]
>> (filter (fn [new-yx]
>> (every? #(< -1 % size) new-yx))
>> (map #(map + yx %) deltas))))
>>
>> This syntax made me scratch my head since I believe it was the first
>> time I saw it.
>
> In case it wasn't clear from Chouser's response, the key difference is
> that this declares two versions of neighbors, one that takes three
> arguments and one that takes four - essentially overloading on arity.
> Here's an example from some of our code at World Singles:
>
> (defn save-row
> "Given a table name (string), a record and an optional
> key-gen function, either insert it after applying the
> key-gen function (if no pk) or update it. In both
> cases, return the pk. The default key-gen function
> is a no-op (identity).
> When operating on a MongoDB collection, the logic is
> much simpler because the pk is always :_id and key
> generation is always handled by MongoDB. Also, we
> always return the entire updated record (since we
> can run functions against the database)."
> ([table record] (save-row table record identity :id 0))
> ([table record key-gen] (save-row table record key-gen :id 0))
> ([table record key-gen pk] (save-row table record key-gen pk 0))
> ([table record key-gen pk retry]
> ...))
>
> Mostly we call this as (save-row :table-name {:some "record"}) but we
> can also supply a key generation function (save-row :table-name {:some
> "record"} add-uuid), for tables that don't have a generated PK column,
> and we can specify the PK name if it isn't :id (save-row :table-row
> {:some "record"} identity :email).
>
> Ignore retry - we need to refactor that into a private helper function
> :) It's part of the machinery that let's automatically retry
> operations on MongoDB if the replica set has no active primary node
> since it can take a while to failover...
>
> Hope that helps?
> --
> Sean A Corfield -- (904) 302-SEAN
> An Architect's View -- http://corfield.org/
> World Singles, LLC. -- http://worldsingles.com/
> Railo Technologies, Inc. -- http://www.getrailo.com/
>
> "Perfection is the enemy of the good."
> -- Gustave Flaubert, French realist novelist (1821-1880)
>
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