From: Robert Klemme <shortcutter@...>
Date: 2009-05-05T02:15:09+09:00
Subject: Re: String#hash changed in Ruby 1.9?

On 04.05.2009 16:48, David Palm wrote:
>>> Any tips on how to replace it?
>> What does it hurt if the hash value of a string does not remain constant 
>> between runs of the application?
> 
> In my case it's pretty bad. I use it in a command line utility to cache rake tasks. I create one cachefile for each directory, naming them using the String#hash of the full path (Dir.pwd.hash). If the hash is different the next time the program runs the cache lookup fails (and I get a new cache file instead of the old one).

Hm...  But you do admit that this is a bit abusive, do you?   Especially 
since there are no guarantees that you won't have any collisions with a 
hash value like the one returned by #hash.

How about storing your cache files with a fixed name in the original 
directory?  Or have a file with metadata (mapping from path to cache 
file name)?

> So, I don't need anything fancy, just an equivalent to Dir.pwd.hash that stay consistent. Do I need to MD5 it? Feels like overkill. Why was this changed in the first place?

That's an interesting question.  I'm curious as well.  Maybe the changes 
are just a side effect of a new - supposedly better - hashing algorithm.

Kind regards

	robert