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From: Paul Rubin <no.email@nospam.invalid>
Newsgroups: comp.lang.forth
Subject: Re: real to rational number
Date: Thu, 20 Apr 2017 18:52:53 -0700
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krishna.myneni@ccreweb.org writes:
> In some instances, such as for the squares of the Wigner 3-j symbols,
> we know in advance that the results are rational numbers. However, on
> a computer, they are often calculated in such a way to give a floating
> point number and it is difficult to find the corresponding rational
> number by hand.

You could use mpfr and do the calculation in exact rational arithmetic
from the beginning.