feat: add `math/base/special/truncbf`

[Amansingh0807]

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Resolves a part of #649

Description

What is the purpose of this pull request?

This pull request:

• This PR adds a C implementation for @stdlib/math/base/special/truncbf.

The package computes the value of a single-precision floating-point number rounded toward zero to n digits in an arbitrary base b.

Implementation Details

Function Signature

float stdlib_base_truncbf( const float x, const int32_t n, const int32_t b );

function truncbf( x, n, b )

Algorithm

The implementation uses the following formula:

truncbf(x, n, b) = trunc(x × b^n) / b^n

It leverages the recently added C implementations of powf (for scaling) and truncf (for truncation) to ensure single-precision accuracy.

Examples

- truncbf( 3.14159f, 2, 10 ); // returns 3.14f
- truncbf( 15.75f, 2, 2 );    // returns 15.75f (Binary base)
- truncbf( 255.99f, 1, 16 );  // returns 255.9375f (Hex base)

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• Resolves a part of #649

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.

No.

Checklist

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

• [x] Read, understood, and followed the contributing guidelines.

AI Assistance

When authoring the changes proposed in this PR, did you use any kind of AI assistance?

• [ ] Yes
• [x] 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

If you answered "yes" to using AI assistance, please provide a short disclosure indicating how you used AI assistance. This helps reviewers determine how much scrutiny to apply when reviewing your contribution. Example disclosures: "This PR was written primarily by Claude Code." or "I consulted ChatGPT to understand the codebase, but the proposed changes were fully authored manually by myself.".

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/truncbf	$\color{red}202/204$ $\color{green}+0.00%$	$\color{red}13/14$ $\color{green}+0.00%$	$\color{green}2/2$ $\color{green}+0.00%$	$\color{red}202/204$ $\color{green}+0.00%$

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

[Amansingh0807]

@kgryte I have addressed all your feedback:

1. Macro Usage: Switched addon.c to use the @stdlib/math/base/napi/ternary macro (and updated dependencies in package.json).
2. Single-Precision: Updated main.c to use single-precision functions (powf, truncf) and headers.
3. Manifest: Cleaned up the src array in manifest.json to only include main.c.

Additionally, I fixed the benchmarks to use @stdlib/math/base/special/trunc and resolved all linting/build errors. All checks are passing now.

[Amansingh0807]

Hi @kgryte Just a quick update: I have squashed the commit history into a single clean commit to facilitate the review.

In addition to the requested fixes (macros, single-precision types), I also performed a strict self-audit and added:

Overflow Protection: Handling cases where the scale factor b^n overflows (returning x to preserve the value).

JS Parity: Enforced strict float32 emulation in the JavaScript implementation to match C behavior exactly.