feat: add C implementation for stats/base/dists/f/pdf

[rautelaKamal]

Description

What is the purpose of this pull request?

This pull request:

• Implements a native C-port for the F Distribution Probability Density Function (@stdlib/stats/base/dists/f/pdf).
• Configures include.gypi, binding.gyp, and manifest.json dependencies via internal N-API mechanisms (STDLIB_MATH_BASE_NAPI_MODULE_DDD_D).
• Validates identical sub-epsilon behavior to pure JS implementation across boundaries, limits, and NaN.
• Introduces robust Boost and Julia test.native.js fixtures to validate the C-port accuracy and benchmarks it.

Related Issues

Does this pull request have any related issues?

This pull request has no related issues.

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

This is a Proof of Concept submission towards my GSoC 2026 application regarding porting distributions and specific math functions to high-performance C native addons.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

AI Assistance

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• Yes
• No

If you answered "yes" above, how did you use AI assistance?

• Code generation (e.g., when writing an implementation or fixing a bug)
• Test/benchmark generation
• Documentation (including examples)
• Research and understanding

Disclosure

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---

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[stdlib-bot]

Coverage Report

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The above coverage report was generated for the changes in this PR.

[rautelaKamal]

Just a quick heads up regarding the minor coverage drop flagged by Codecov:

The native.js file is showing 0% function coverage because the addon.node binary correctly skips compilation during the CI coverage step, which triggers the expected opts.skip = true fallback inside test.native.js. The math logic is fully tested and verified when the native addon actually builds!

Also, the drop in ibeta_power_terms.js relates to the original pure JavaScript implementations and was untouched in this PR. @Planeshifter

[Neerajpathak07]

@rautelaKamal FYI: I think you have misunderstood what we do for adding native implementation. Here we expect to add the corresponding C files for benchmark, examples and the main implementation alongside the relevant dependencies and documentations.
Take a look at a few of the merged PR's on how this is done.
For eg:- refer to https://github.com/stdlib-js/stdlib/pull/10839/changes

[rautelaKamal]

@Neerajpathak07 Thank you for catching this and pointing me to the reference PR! I totally misunderstood the scope, I was focused solely on evaluating the N-API/Node.js boundary and completely neglected the standalone C ecosystem deliverables.

I have just pushed an update that adds the benchmark/c/ and examples/c/ directories, the src/Makefile for cleanup, and the full C APIs documentation section in the README.md.

Really appreciate you taking the time to explain the standard.Please let me know if there's anything else I missed!

[Lokeshranjan8]

@rautelaKamal Update your commit message

feat(stats/base/dists/f/pdf): add native C addon for evaluating the PDF

to the following

feat: add C implementation for stats/base/dists/f/pdf