feat: add `constants/float64/inv-two-pi` by Amansingh0807 · Pull Request #8982 · stdlib-js/stdlib

Amansingh0807 · 2025-12-12T02:57:58Z

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Description

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This pull request:

add constants/float64/inv-two-pi

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stdlib-bot · 2025-12-12T02:59:40Z

Coverage Report

Package	Statements	Branches	Functions	Lines
constants/float64/inv-two-pi	$\color{green}48/48$ $\color{green}+0.00%$	$\color{green}1/1$ $\color{green}+0.00%$	$\color{green}0/0$ $\color{green}+0.00%$	$\color{green}48/48$ $\color{green}+0.00%$

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

Amansingh0807 · 2025-12-12T03:03:13Z

Hi @Neerajpathak07!
Just wanted to let you know that I have added the single precision and double precision versions of inv-two-pi as discussed.
Everything is pushed and the PRs are ready.
Let me know if you'd like anything adjusted.

Neerajpathak07 · 2025-12-12T03:58:52Z

lib/node_modules/@stdlib/constants/float64/inv-two-pi/lib/index.js

+* @default 0.15915494309189535
+* @see [Wikipedia]{@link https://en.wikipedia.org/wiki/Pi}
+*/
+var FLOAT64_INV_TWO_PI = 0.15915494309189533576888376337251436203445964574045644874766734405889679763422653509534861042142103174415371554; // eslint-disable-line max-len


Why is the value exceeding the precision limit. The return value should be the same as the set default value.

Neerajpathak07 · 2025-12-12T03:59:20Z

lib/node_modules/@stdlib/constants/float64/inv-two-pi/lib/index.js

+* @default 0.15915494309189535
+* @see [Wikipedia]{@link https://en.wikipedia.org/wiki/Pi}
+*/
+var FLOAT64_INV_TWO_PI = 0.15915494309189533576888376337251436203445964574045644874766734405889679763422653509534861042142103174415371554; // eslint-disable-line max-len


Suggested change

var FLOAT64_INV_TWO_PI = 0.15915494309189533576888376337251436203445964574045644874766734405889679763422653509534861042142103174415371554; // eslint-disable-line max-len

var FLOAT64_INV_TWO_PI = 0.15915494309189535;

Neerajpathak07 · 2025-12-12T04:02:17Z

...e_modules/@stdlib/constants/float64/inv-two-pi/include/stdlib/constants/float64/inv_two_pi.h

+/**
+* Macro for the inverse of 2π (1/(2π)).
+*/
+#define STDLIB_CONSTANT_FLOAT64_INV_TWO_PI 0.15915494309189533577


Why is the C header file giving out different return value.

I'm interested in knowing where this value is coming from did you take any reference you would like to share?

Amansingh0807 · 2025-12-12T04:18:13Z

Thanks for the review @Neerajpathak07!

Regarding the long value: It is actually the arbitrary-precision decimal expansion of 1 / (2π). It wasn't calculated using the standard Math.PI, but generated using a high-precision tool (mpmath) to ensure the literal is the exact mathematical "source of truth".

The value in the C header (...3577) appears to be the same value but rounded to 20 decimal places (since the next digit in the expansion is 8, it rounded up ...76 to ...77).

However, I agree with you for practical float64 representation in JS, the truncated version avoids confusion. I have updated the value to match the standard 15-17 digit precision as suggested.

Neerajpathak07 · 2025-12-12T04:28:10Z

lib/node_modules/@stdlib/constants/float64/inv-two-pi/README.md

+</section>
+
+<!-- /.related -->
+


Since you have added an C header file you'll have to add the documentation for C usage as well. To address the macro version.

feat: add constants/float64/inv-two-pi

7a45af2

stdlib-bot added the Needs Review A pull request which needs code review. label Dec 12, 2025

Amansingh0807 added 2 commits December 12, 2025 09:06

feat: add constants/float64/inv-two-pi

cc26a22

fix: add include directory to package.json

fdcc9c9

Neerajpathak07 reviewed Dec 12, 2025

View reviewed changes

fix: correct precision for float64 inv-two-pi to match IEEE 754

2c4a581

Neerajpathak07 reviewed Dec 12, 2025

View reviewed changes

docs: add C API documentation for inv-two-pi constant

e44bf0b

kgryte added Feature Issue or pull request for adding a new feature. Needs Discussion Needs further discussion. labels Dec 16, 2025

Amansingh0807 mentioned this pull request Dec 16, 2025

Office Hours (2025-12-16) stdlib-js/meetings#64

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feat: add `constants/float64/inv-two-pi`#8982

feat: add `constants/float64/inv-two-pi`#8982
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	var FLOAT64_INV_TWO_PI = 0.15915494309189533576888376337251436203445964574045644874766734405889679763422653509534861042142103174415371554; // eslint-disable-line max-len
	var FLOAT64_INV_TWO_PI = 0.15915494309189535;

		</section>

		<!-- /.related -->

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