Iterable.containsWith — API

Iterable.containsWithconsteffect/Iterable.ts:1061

<A>(isEquivalent: (self: A, that: A) => boolean): {
  (a: A): (self: Iterable<A>) => boolean
  (self: Iterable<A>, a: A): boolean
}

Returns a function that checks if an Iterable contains a given value using a provided isEquivalent function.

Example (Checking membership with custom equivalence)

import { Iterable } from "effect"

// Custom equivalence for objects
const byId = (a: { id: number }, b: { id: number }) => a.id === b.id
const containsById = Iterable.containsWith(byId)

const users = [{ id: 1 }, { id: 2 }]
const hasUser1 = containsById(users, { id: 1 })
console.log(hasUser1) // true (same id)

// Case-insensitive string comparison
const caseInsensitive = (a: string, b: string) =>
  a.toLowerCase() === b.toLowerCase()
const containsCaseInsensitive = Iterable.containsWith(caseInsensitive)

const words = ["Hello", "World"]
const hasHello = containsCaseInsensitive(words, "hello")
console.log(hasHello) // true

// Approximate number comparison
const approxEqual = (a: number, b: number) => Math.abs(a - b) < 0.1
const containsApprox = Iterable.containsWith(approxEqual)

const values = [1.0, 2.0, 3.0]
const hasAlmostTwo = containsApprox(values, 2.05)
console.log(hasAlmostTwo) // true

elements

Source effect/Iterable.ts:106112 lines

export const containsWith = <A>(isEquivalent: (self: A, that: A) => boolean): {
  (a: A): (self: Iterable<A>) => boolean
  (self: Iterable<A>, a: A): boolean
} =>
  dual(2, (self: Iterable<A>, a: A): boolean => {
    for (const i of self) {
      if (isEquivalent(a, i)) {
        return true
      }
    }
    return false
  })

Referenced by 1 symbols

Iterable.contains