Getting the hash of any value easily?

[Timon Gehr via Digitalmars-d]

On 07/31/2014 09:40 PM, H. S. Teoh via Digitalmars-d wrote:
> The definition of hash function requires that its output depend only on its
> input(s), so why can't it be pure?

For example, because it might actually be random on the first invocation 
and cached later. :-)

http://hg.openjdk.java.net/jdk7/jdk7/jdk/file/tip/src/share/classes/java/lang/Object.java#l101

http://blogs.tedneward.com/CommentView,guid,eca26c5e-307c-4b7c-931b-2eaf5b176e98.aspx 
(caution, broken script, didn't find a better source to quote quickly.)