What one would want is object -> fixnum, where the fixnum identifies the type of the object. If the fixnums are not too big, one could dispatch by means of a vector reference.
Jos > -----Original Message----- > From: users-boun...@racket-lang.org > [mailto:users-boun...@racket-lang.org] On Behalf Of Thomas Chust > Sent: 13 June 2011 17:11 > To: Stephan Houben > Cc: Racket Users > Subject: Re: [racket] dispatch on type > > 2011/6/13 Stephan Houben <steph...@planet.nl>: > > [...] > > I have code like this which dispatches on > > the type of a homogenous vector: > > [...] > > I was wondering if there is a more efficient way to > > do this, one which doesn't involve a linear scan > > over all possible types. I presume that at the C level > > there is a "type tag" associated with any of these types; > > is it possible to access this from the Racket level? > > [...] > > Hello Stephan, > > since everything can be interpreted as a structure in Racket, one > thing you could do is dispatch on the name of structure types: > > (define (identify v) > (case (vector-ref (struct->vector v) 0) > ((struct:byte-string) "bytes") > ((struct:u16vector) "small words") > (else "whatever"))) > > However, whether this will really result in a performance gain I don't > know. > > Ciao, > Thomas > > > -- > When C++ is your hammer, every problem looks like your thumb. > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/users _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
