Ha, that makes sense. I had the (apparently wrong) idea that a thunk would be compiled to a ready to use procedure and would be immediately available at run time. Thanks. Jos
> -----Original Message----- > From: robby.find...@gmail.com > [mailto:robby.find...@gmail.com] On Behalf Of Robby Findler > Sent: 18 July 2010 15:39 > To: Jos Koot > Cc: plt-scheme > Subject: Re: [racket] hash-ref > > It is for performance reasons. Specifically you can avoid > creating the procedure over and over (if you're calling > hash-ref over and over). > > Robby > > On Sunday, July 18, 2010, Jos Koot <jos.k...@telefonica.net> wrote: > > > > > > > > > > > > (hash-ref > > a-hash a-key a-value) > > In the past > > a-value was required to be a procedure. > > Now it can > > be anything. > > > > Nice. > > Two caveats > > though. > > 1. If the > > value of a-value happens to be a procedure to be stored, it may > > unintentionally be called. > > 2. a-value > > may be an expresssion that takes much computation. This > computation is > > repeated every time the hash-ref line is evaluated. > > > > Simply > > helped of course: I make it a habbit always to write or to > have macros > > expand > > to: > > (hash-ref a-hash a-key (lambda () > > a-value)) > > > > In short, I do not well understand the reason to relax the > contract of > > hash-ref and hash-ref!. > > Jos > > > > > > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
