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Re: [Scheme-reports] Implied equality
- To: Biep <scheme@x>
- Subject: Re: [Scheme-reports] Implied equality
- From: John Cowan <cowan@x>
- Date: Sun, 6 Jan 2013 12:27:33 -0500
- Cc: scheme-reports <scheme-reports@x>
- In-reply-to: <1480517702.266076.1357487075380.JavaMail.email@example.com>
- References: <firstname.lastname@example.org> <646005380.190332.1356182404191.JavaMail.email@example.com> <CAMMPzYPSnYC8fWKit844AhD8KKxAKx6Aa9Q-=qEYeVxspCAx7w@mail.gmail.com> <1480517702.266076.1357487075380.JavaMail.firstname.lastname@example.org>
> But in that case the equations for make-polar are false, aren't they?
> z may be exact on input and inexact on output.
Well, yes. But that point is made immediately thereafter, and extends
only to the representation of numbers as exact or inexact, not to the
numbers themselves. Furthermore, it is not a necessary truth: Pure
(which shares Scheme's numeric tower) has both rectangular and polar
representations of complex numbers internally, so the equivalent of
(make-polar x3 x4), namely x3 <: x4, can return an exact value for
exact arguments in the appropriate range.
John Cowan cowan@x
At times of peril or dubitation, http://www.ccil.org/~cowan
Perform swift circular ambulation,
With loud and high-pitched ululation.
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