Re: [pure-lang-users] math.pure

[John C. <co...@cc...>]

Eddie Rucker scripsit:

> LOL! I noticed atanh is not defined in mzscheme so had to look it up.
> (define (atanh x) (* .5 (log (/ (+ 1.0 x) (- 1.0 x)))))

Here is the Common Lisp discussion of where the branch cuts of the
transcendental functions are: http://tinyurl.com/5rbsng .  It claims
that the correct function is:

(define (atanh z) (log (* (+ 1 z) (sqrt (- 1 (/ 1 (expt z 2)))))))

Clisp reports #C(-0.54930615 1.5707964) for (atanh -2).

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