PHP's expm1 in TypeScript

How to use

Install via yarn add locutus and import: import { expm1 } from 'locutus/php/math/expm1'.

Or with CommonJS: const { expm1 } = require('locutus/php/math/expm1')

Use a bundler that supports tree-shaking so you only ship the functions you actually use. Vite, webpack, Rollup, and Parcel all handle this. For server-side use this is less of a concern.

Examples

These examples are extracted from test cases that automatically verify our functions against their native counterparts.

#	code	expected result
1	expm1(1e-15)	1.0000000000000007e-15

Notes

• Precision ‘n’ can be adjusted as desired

Here's what our current TypeScript equivalent to PHP's expm1 looks like.

TSTypeScript JSJavaScript TSStandalone TS JSStandalone JS

Copy code

export function expm1(x: number): number {
  //      discuss at: https://locutus.io/php/expm1/
  // parity verified: PHP 8.3
  //     original by: Brett Zamir (https://brett-zamir.me)
  //     improved by: Robert Eisele (https://www.xarg.org/)
  //          note 1: Precision 'n' can be adjusted as desired
  //       example 1: expm1(1e-15)
  //       returns 1: 1.0000000000000007e-15

  return x < 1e-5 && x > -1e-5 ? x + 0.5 * x * x : Math.exp(x) - 1
}

export function expm1(x) {
  //      discuss at: https://locutus.io/php/expm1/
  // parity verified: PHP 8.3
  //     original by: Brett Zamir (https://brett-zamir.me)
  //     improved by: Robert Eisele (https://www.xarg.org/)
  //          note 1: Precision 'n' can be adjusted as desired
  //       example 1: expm1(1e-15)
  //       returns 1: 1.0000000000000007e-15

  return x < 1e-5 && x > -1e-5 ? x + 0.5 * x * x : Math.exp(x) - 1
}

Improve this function

Locutus is a community effort following The McDonald's Theory: we ship first iterations, hoping others will improve them. If you see something that could be better, we'd love your contribution.

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