[R-pkg-devel] How to get arbitrary precise inputs from R for an Rcpp package?

[Vladimir Dergachev]

I see there are existing extended precision packages: Ryacas and Rmpfr, 
you might want to take a look at them and their representation of numbers 
with higher precision than a double.

best

Vladimir Dergachev

On Fri, 19 Jul 2024, Khue Tran wrote:

> Hi,
>
> I am trying to create an Rcpp package that involves arbitrary precise
> calculations. The function to calculate e^x below with 100 digits precision
> works well with integers, but for decimals, since the input is a double,
> the result differs a lot from the arbitrary precise result I got on
> Wolfram.
>
> I understand the results are different since 0.1 cannot be represented
> precisely in binary with limited bits. It is possible to enter 1 then 10
> and get the multiprecision division of these two integers to attain a more
> precise 0.1 in C++, but this method won't work on a large scale. Thus, I am
> looking for a general solution to get more precise inputs?