Getting the hash of any value easily?

[H. S. Teoh via Digitalmars-d]

On Thu, Jul 31, 2014 at 07:08:16PM +0000, Brian Schott via Digitalmars-d wrote:
> On Thursday, 31 July 2014 at 17:39:43 UTC, H. S. Teoh via Digitalmars-d
> wrote:
> >It's about time somebody noticed this!!
> >
> >Why don't we just expose druntime's core.internal.hash.hashOf()
> >function somewhere? It's not as though it isn't already in druntime,
> >so the function is already present in the executable, we just need a
> >public declaration of it somewhere that users can make use of.
> >
> >Not to mention, it's already a template function that correctly
> >calculates the hash of various built-in types.
> >
> >
> >T
> 
> I've often just put "import core.internal.hash;" in my code.
> 
> Once we get this solved we need to work on the fact that many hash
> generation functions are not pure.

I'm not sure I understand why. Un- at safe (probably should be @trusted) I
can understand, since you basically have to treat arbitrary typed data
as ubyte[] in order to compute the hash, but impure? I don't see it. The
definition of hash function requires that its output depend only on its
input(s), so why can't it be pure?


> (Object.toHash not being pure prevents a lot of containers from being
> used in pure templated code)

Yeah, this is one of the things that prompted us to move towards
removing toHash from Object.


T

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