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Re: implementation categories, exact rationals



Aubrey Jaffer scripsit:

>  | > A case could be made if (expt -26. 1/3) returned -2.9624960684073702;
>  | > but I know of no Scheme implementation that does so.
>  | 
>  | Why would that be desirable?
> 
> Because it is the cube root of -26.  A better example is:
> (expt -27 1/3) ==> -3

-3 is *a* cube root of 27, but not the *principal* cube root.  Consider the
third part of Quux's Tripartite Acceptance Test:

1) the value of T is T (or in Scheme, of #t is #t)

2) the value of (/ (factorial 1000) (factorial 999)) is 1000 (given the
usual iterative definition of factorial)

3) the value of (atanh -2) is a complex number (if it is the right complex
number, approximately -0.54930615+1.5707964i, so much the better)

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