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Re: [Scheme-reports] exact-closed in features list

Per Bothner scripsit:

> Frankly, this seems weird.  I would expect / to give exact values
> given exact inputs if an implementation has this property.

Implementing / requires support for rationals, whereas implementing
support for +, -, * requires only support for bignums.  (Of course,
technically no operation is closed over even the integers because of
implementation restrictions.)

> Wikipedia defines "Algebraic operation" to include "taking roots".

That was an oversight on my part.  I'll go with a variant of your
second wording:

>    The algebraic operations +, -, *, and expt where the second
>    argument is a non-negative integer all produce exact values given
>    exact inputs.

John Cowan          http://www.ccil.org/~cowan        cowan@x
Knowledge studies others / Wisdom is self-known;
Muscle masters brothers / Self-mastery is bone;
Content need never borrow / Ambition wanders blind;
Vitality cleaves to the marrow / Leaving death behind.    --Tao 33 (Bynner)

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