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Re: Arbitrary precision integer arithmetic


From: Colin Macdonald
Subject: Re: Arbitrary precision integer arithmetic
Date: Sat, 8 Sep 2018 23:42:07 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1

On 2018-09-07 10:21 PM, Etienne Grossmann wrote:
Hi again,

sorry, I didn't express myself clearly, and I didn't know about the sym() function, only the vpa() function.

Let's say I want to compute 423^567 exactly.

With the vpa() function, I have to specify the length of the result, as in vpa (vpa(423)^567, 1500).

The correct approach is to use the sym() function:  with the sym() function, sym('423^567') gives me the correct answer.

Sorry I'm late to this party. You're right; vpa is not appropriate here: that is generally for variable precision floating point (i.e., inexact with rounding).

Your example is most easily done as:

sym(423)^567

And if you need to type a large integer, use strings:

sym('12345682349871248651953253257235')^sym('123123124125')

- - - - -

intinf looks like it was great fun to write so far! If you're into this sort of thing, I can definitely use help with the Symbolic package---and even more so with upstream SymPy that powers it.

The Interval package also involves @classes and overloading everything :)

cheers,
Colin



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