[RFC]: Add implementation for modified Bessel function of the second kind of any real-valued order ( `besselk` )

[shubham220420]

Description

This RFC proposes to add implementation of modified Bessel function of the second kind of any real-valued order.

currently I have found a few references for its implementation -
1.SciPy
2.BoostOrg

Related Issues

Related issues # , # , and # .

Questions

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Other

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Checklist

• I have read and understood the Code of Conduct.
• Searched for existing issues and pull requests.
• The issue name begins with RFC:.

[shubham220420]

hey maintainers @kgryte & @Planeshifter I would like to know your thoughts about the implementations for this feature, and if this is a required function in the library right now.
Also I want to work on this so will be seeking your guidance if this RFC is accepted.

[kgryte]

@shubham220420 I suggest understanding how our current set of Bessel functions is implemented. You'll likely find the answer to your question regarding reference implementation there.

[shubham220420]

hey @kgryte I've done a bit of research on this, according to boost math library the implementation of bessel_kn is a recursive function of bessel_k0 & bessel_k1, so does this issue be completed in multiple parts by first adding k0 & k1 .

[kgryte]

Yes, I would suggest starting with k0 and k1.

[shubham220420]

Hey @kgryte I have added the initial implementation for k0 in #9954, kindly look into it whenever possible, thanks.