On Mon, Oct 1, 2012 at 4:45 PM, Timothy Baldridge <tbaldri...@gmail.com>wrote:
> I've thought about this as well. Coming from the .NET world I'm quite > familiar with the Linq.Expression namespace. I too have wondered about > this. For those who are not familiar with how IQueryable<T> works in Linq, > it's something like the following (in clojure): > > > (def query (q (db :people) > (where #(> (:age %) 21)) > :last-name > distinct)) > > The (db :people) call will return a IQueryable object. The q macro will > then take all the clauses in the query, wrap them up into an AST, and then > create a lazy seq. At this point in the code, nothing has been executed. > Upon calling (first query), the q macro hands the AST to the IQueryable > object, and then calls Execute on the object. Execute does whatever it > pleases with the AST, and then returns a lazy seq of the results. > > A C# tutorial on this, is available here ( > http://wekeroad.com/2007/07/02/linq-how-to-use-linq-to-query-just-about-anything/ > ) > > I see this fitting into the Clojure ecosystem in a very interesting way: > > Seq abstraction - > Lazy evaluation > Must run on the local CPU (for map, reduce, etc.) > Must run in order > Data provider can't influence execution > > Reducers - > Data provider can influence execution > Must run on the local CPU > Can run in any order > > IQueryable abstraction - > Data provider has full control over execution > Code can be run anywhere > Provider must compile code. > > > Example providers of IQueryable: > > Entity Framework (Linq over SQL) > Linq to XML (Linq over XML) > Linq to GPU (run queries on a graphics processor) > http://brahma.ananthonline.net/ > I've also seen index providers for in-memory data structures > > Not to nitpick, but Linq to XML is based on Linq to objects entirely (no IQueryable, juste vanilla IEnumerables). There also used to be a "Linq to Map reduce" (called DryadLINQ, then Linq to HPC, then "let's forget about this and hop on the hadoop bandwagon") which looked a lot like Scalding (Scala over Cascading), only with IQueryable goodies. To my - naive - knowledge of clojure macros, writing an provider in clojure would be a lot easier than it is in C# (or even with F# quotations). -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
