COUPLING(3pm)

💫 COUPLING(3pm) 💫

okay so this is COUPLING, living in the User Contributed Perl Documentation section of your man pages, and bestie it is exactly what it sounds like: PDL's lil doorway into the GSL special functions. 🎀

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✨ NAME ✨

PDL::GSLSF::COUPLING — the PDL interface to GSL Special Functions. that's it, that's the whole name, slay 💅

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🌸 DESCRIPTION 🌸

so basically? this is an interface to the Special Function package that lives inside the GNU Scientific Library. you bring the PDL, GSL brings the fancy math, and this module is the group chat they text in. no cap. 🦋

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🔥 FUNCTIONS 🔥

🎀 gsl_sf_coupling_3j

the signature, verbatim, look at her:

Signature: (ja(); jb(); jc(); ma(); mb(); mc(); double [o]y(); double [o]e())

so this one does 3j Symbols, and the layout is:

(ja jb jc) over (ma mb mc).

and here's the important heads-up, bestie: gsl_sf_coupling_3j does not process bad values. if the bad-value flag is set on any of the input ndarrays, it will set the bad-value flag on all of the output ndarrays. so like… it's not gonna quietly fix it for you, it's gonna tell on you. 💀

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🦋 gsl_sf_coupling_6j

signature time:

Signature: (ja(); jb(); jc(); jd(); je(); jf(); double [o]y(); double [o]e())

6j Symbols, arranged like this:

(ja jb jc) over (jd je jf).

same energy as her sister up there: gsl_sf_coupling_6j does not process bad values, and if the bad-value flag is set on any input ndarray it sets it on all the output ndarrays. it's giving consistency, honestly. 😭

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💜 gsl_sf_coupling_9j

the biggest one, the main character, the signature:

Signature: (ja(); jb(); jc(); jd(); je(); jf(); jg(); jh(); ji(); double [o]y(); double [o]e())

9j Symbols, stacked three deep:

(ja jb jc) over (jd je jf) over (jg jh ji).

and you already know what I'm about to say: gsl_sf_coupling_9j does not process bad values. bad-value flag set on any input ndarray → flag set on all the output ndarrays. every time. iconic behavior honestly. 👑

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👑 AUTHOR 👑

this file is copyright (C) 1999 Christian Pellegrin <chri@infis.univ.trieste.it> — all rights reserved, and ngl there is no warranty. 💀

you are allowed to redistribute this software / documentation under certain conditions. for the details, go read the file COPYING in the PDL distribution. and if this file ever gets separated from the rest of the PDL distribution, the copyright notice should stay included in the file — like, don't orphan her, she needs her paperwork. 🥺

also shoutout to G. Jungman, who wrote the GSL SF modules. king behavior. 🫶

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✨ and that's the whole page, bestie! this was perl v5.38.2, dated 2024-04-10. go forth and couple those angular momenta, ily 💖🌸🎀