Re: [Sbcl-help] Optimizing a simple Common Lisp Gibbs sampler program

[Faheem M. <fa...@fa...>]

Hi Stephan,

Thanks for your reply.

On Thu, 31 May 2012, cri...@cs... wrote:

> Hi Fareen,
>
> the (the double-float ...) tells the compiler that you insist that the
> result is a double-float; though you may lie to the compiler if x assumes
> non-appropriate values for this declaration.
>
> I see in the Stackoverflow thread that you want to declrare x as beaing a
> d-f >= 0.0. If this is the case than you can try:
>
> (declare (type (double-float 0.0 *) x))

If this declaration says that x is a double float which is greater than or 
equal to 0, then that seems like a good way to resolve the problem.

Can you give me a reference for this syntax? Thanks.

> Then you should also be able to remove the (the double-float ...) since
> the compiler should be able to infer that the result can only be a
> double-float. Furthermore you will get automatically a type/range-check
> for the correct values of x.

Oh, the compiler will automatically put in a runtime check that x >= 0? 
Interesting.

> Hope this helps.

Yes, thanks.

> Best regards,
> Stephan

Regards, Faheem.