Re: (cos (scale-float 1d0 120)) incorrect

[Sam S. <sd...@gn...>]

Please file a bug report on SF.net.
Thanks.

> * Raymond Toy <gbl...@tz...> [2013-11-19 13:49:56 -0800]:
>
> Clisp 2.49 on a Linux Ubuntu box says:
>
> [1]> (cos (scale-float 1d0 120))
> 1.0d0
>
> The true answer is closer to -0.92.  Cmucl and ccl produce this
> answer.  Maxima says this is the correct answer.
>
> I think the issue is that pi reduction is not done to full precision.
>
> Using long-floats, clisp still produces 1L0, but making
> long-float-digits 128 gives the correct answer.
>
> Note also that (scale-float 1d0 120) can be represented exactly as an
> IEEE754 double precision value, and that IEEE754 doubles are not
> approximations.  They are exact rationals (of a certain form).
>
> Ray
>
>
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