On Saturday, August 3, 2019 at 1:36:01 PM UTC+8, Jon Zeppieri wrote: > > On Sat, Aug 3, 2019 at 12:52 AM Jesse Wang <[email protected] > <javascript:>> wrote: > > > > If I want to turn the hash code into array index in a hash table, do I > need to > > apply another uniform hash function such as md5 on the result of > equal-hash-code? > > > > That wouldn't accomplish anything. The defining feature of a function > is that the output depends solely on the input. Applying the same > function to colliding hash codes will get you more colliding hash > codes, only at a higher cost. >
I think you are right here. > > If you're going to implement your own hash tables instead of using the > ones that Racket provides, you can use whatever hash function you > want, but in that case you want to start with the key itself, not with > the result of Racket's hash function. Hash functions, by their very > nature, tend to discard information. If you start with the result of > Racket's hash functions, you're not going to be able to do better than > them. What I want is a uniform hash function for different types. Racket's equal-hash-code seems to give non-uniform hash codes for different types of primitive types, so I wonder how Racket achieves good performance in a hash table with different primitive type keys at the same time... -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/fc2ded74-043e-413c-b1da-6b3a06837f8d%40googlegroups.com.
