Python's math.isclose in TypeScript

How to use

Install via yarn add locutus and import: import { isclose } from 'locutus/python/math/isclose'.

Or with CommonJS: const { isclose } = require('locutus/python/math/isclose')

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	isclose(0.1 + 0.2, 0.3)	true
2	isclose(1000.0, 1001.0, 0.01)	true
3	isclose(1.0, 1.1, 1e-9, 0)	false

Notes

• Tests whether two numbers are close within relative/absolute tolerances.

Here's what our current TypeScript equivalent to Python's math.isclose looks like.

TSTypeScript JSJavaScript TSStandalone TS JSStandalone JS

Copy code

export function isclose(
  a: number | string,
  b: number | string,
  relTol: number | string = 1e-9,
  absTol: number | string = 0,
): boolean {
  //      discuss at: https://locutus.io/python/isclose/
  // parity verified: Python 3.12
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Tests whether two numbers are close within relative/absolute tolerances.
  //       example 1: isclose(0.1 + 0.2, 0.3)
  //       returns 1: true
  //       example 2: isclose(1000.0, 1001.0, 0.01)
  //       returns 2: true
  //       example 3: isclose(1.0, 1.1, 1e-9, 0)
  //       returns 3: false

  const left = Number(a)
  const right = Number(b)
  const relative = Number(relTol)
  const absolute = Number(absTol)

  if (!Number.isFinite(relative) || !Number.isFinite(absolute) || relative < 0 || absolute < 0) {
    throw new RangeError('isclose(): tolerances must be non-negative finite numbers')
  }

  if (Number.isNaN(left) || Number.isNaN(right)) {
    return false
  }
  if (left === right) {
    return true
  }
  if (!Number.isFinite(left) || !Number.isFinite(right)) {
    return false
  }

  const difference = Math.abs(left - right)
  const threshold = Math.max(relative * Math.max(Math.abs(left), Math.abs(right)), absolute)
  return difference <= threshold
}

export function isclose(a, b, relTol = 1e-9, absTol = 0) {
  //      discuss at: https://locutus.io/python/isclose/
  // parity verified: Python 3.12
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Tests whether two numbers are close within relative/absolute tolerances.
  //       example 1: isclose(0.1 + 0.2, 0.3)
  //       returns 1: true
  //       example 2: isclose(1000.0, 1001.0, 0.01)
  //       returns 2: true
  //       example 3: isclose(1.0, 1.1, 1e-9, 0)
  //       returns 3: false

  const left = Number(a)
  const right = Number(b)
  const relative = Number(relTol)
  const absolute = Number(absTol)

  if (!Number.isFinite(relative) || !Number.isFinite(absolute) || relative < 0 || absolute < 0) {
    throw new RangeError('isclose(): tolerances must be non-negative finite numbers')
  }

  if (Number.isNaN(left) || Number.isNaN(right)) {
    return false
  }
  if (left === right) {
    return true
  }
  if (!Number.isFinite(left) || !Number.isFinite(right)) {
    return false
  }

  const difference = Math.abs(left - right)
  const threshold = Math.max(relative * Math.max(Math.abs(left), Math.abs(right)), absolute)
  return difference <= threshold
}

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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