Skip to main content Link Search Menu Expand Document (external link)
effect

Predicate overview

Added in v2.0.0

Table of contents

combinators

and

Combines two predicates into a new predicate that returns true if both of the predicates returns true.

Signature

export declare const and: {
  <A, C extends A>(that: Refinement<A, C>): <B extends A>(self: Refinement<A, B>) => Refinement<A, B & C>
  <A, B extends A, C extends A>(self: Refinement<A, B>, that: Refinement<A, C>): Refinement<A, B & C>
  <A>(that: Predicate<A>): (self: Predicate<A>) => Predicate<A>
  <A>(self: Predicate<A>, that: Predicate<A>): Predicate<A>
}

Example

import * as P from "effect/Predicate"

const minLength = (n: number) => (s: string) => s.length >= n
const maxLength = (n: number) => (s: string) => s.length <= n

const length = (n: number) => P.and(minLength(n), maxLength(n))

assert.deepStrictEqual(length(2)("aa"), true)
assert.deepStrictEqual(length(2)("a"), false)
assert.deepStrictEqual(length(2)("aaa"), false)

Added in v2.0.0

eqv

Signature

export declare const eqv: {
  <A>(that: Predicate<A>): (self: Predicate<A>) => Predicate<A>
  <A>(self: Predicate<A>, that: Predicate<A>): Predicate<A>
}

Added in v2.0.0

implies

Signature

export declare const implies: {
  <A>(that: Predicate<A>): (self: Predicate<A>) => Predicate<A>
  <A>(self: Predicate<A>, that: Predicate<A>): Predicate<A>
}

Added in v2.0.0

mapInput

Given a Predicate<A> returns a Predicate<B>

Signature

export declare const mapInput: {
  <B, A>(f: (b: B) => A): (self: Predicate<A>) => Predicate<B>
  <A, B>(self: Predicate<A>, f: (b: B) => A): Predicate<B>
}

Example

import * as P from "effect/Predicate"
import * as N from "effect/Number"

const minLength3 = P.mapInput(N.greaterThan(2), (s: string) => s.length)

assert.deepStrictEqual(minLength3("a"), false)
assert.deepStrictEqual(minLength3("aa"), false)
assert.deepStrictEqual(minLength3("aaa"), true)
assert.deepStrictEqual(minLength3("aaaa"), true)

Added in v2.0.0

nand

Signature

export declare const nand: {
  <A>(that: Predicate<A>): (self: Predicate<A>) => Predicate<A>
  <A>(self: Predicate<A>, that: Predicate<A>): Predicate<A>
}

Added in v2.0.0

nor

Signature

export declare const nor: {
  <A>(that: Predicate<A>): (self: Predicate<A>) => Predicate<A>
  <A>(self: Predicate<A>, that: Predicate<A>): Predicate<A>
}

Added in v2.0.0

not

Negates the result of a given predicate.

Signature

export declare const not: <A>(self: Predicate<A>) => Predicate<A>

Example

import * as P from "effect/Predicate"
import * as N from "effect/Number"

const isPositive = P.not(N.lessThan(0))

assert.deepStrictEqual(isPositive(-1), false)
assert.deepStrictEqual(isPositive(0), true)
assert.deepStrictEqual(isPositive(1), true)

Added in v2.0.0

or

Combines two predicates into a new predicate that returns true if at least one of the predicates returns true.

Signature

export declare const or: {
  <A>(that: Predicate<A>): (self: Predicate<A>) => Predicate<A>
  <A>(self: Predicate<A>, that: Predicate<A>): Predicate<A>
}

Example

import * as P from "effect/Predicate"
import * as N from "effect/Number"

const nonZero = P.or(N.lessThan(0), N.greaterThan(0))

assert.deepStrictEqual(nonZero(-1), true)
assert.deepStrictEqual(nonZero(0), false)
assert.deepStrictEqual(nonZero(1), true)

Added in v2.0.0

xor

Signature

export declare const xor: {
  <A>(that: Predicate<A>): (self: Predicate<A>) => Predicate<A>
  <A>(self: Predicate<A>, that: Predicate<A>): Predicate<A>
}

Added in v2.0.0

combining

all

Signature

export declare const all: <A>(collection: Iterable<Predicate<A>>) => Predicate<readonly A[]>

Added in v2.0.0

product

Signature

export declare const product: <A, B>(self: Predicate<A>, that: Predicate<B>) => Predicate<readonly [A, B]>

Added in v2.0.0

productMany

Signature

export declare const productMany: <A>(
  self: Predicate<A>,
  collection: Iterable<Predicate<A>>
) => Predicate<readonly [A, ...A[]]>

Added in v2.0.0

elements

every

Signature

export declare const every: <A>(collection: Iterable<Predicate<A>>) => Predicate<A>

Added in v2.0.0

some

Signature

export declare const some: <A>(collection: Iterable<Predicate<A>>) => Predicate<A>

Added in v2.0.0

guards

hasProperty

Checks whether a value is an object containing a specified property key.

Signature

export declare const hasProperty: {
  <P extends PropertyKey>(property: P): (self: unknown) => self is { [K in P]: unknown }
  <P extends PropertyKey>(self: unknown, property: P): self is { [K in P]: unknown }
}

Added in v2.0.0

isBigInt

Tests if a value is a bigint.

Signature

export declare const isBigInt: (input: unknown) => input is bigint

Example

import { isBigInt } from "effect/Predicate"

assert.deepStrictEqual(isBigInt(1n), true)

assert.deepStrictEqual(isBigInt(1), false)

Added in v2.0.0

isBoolean

Tests if a value is a boolean.

Signature

export declare const isBoolean: (input: unknown) => input is boolean

Example

import { isBoolean } from "effect/Predicate"

assert.deepStrictEqual(isBoolean(true), true)

assert.deepStrictEqual(isBoolean("true"), false)

Added in v2.0.0

isDate

A guard that succeeds when the input is a Date.

Signature

export declare const isDate: (input: unknown) => input is Date

Example

import { isDate } from "effect/Predicate"

assert.deepStrictEqual(isDate(new Date()), true)

assert.deepStrictEqual(isDate(null), false)
assert.deepStrictEqual(isDate({}), false)

Added in v2.0.0

isError

A guard that succeeds when the input is an Error.

Signature

export declare const isError: (input: unknown) => input is Error

Example

import { isError } from "effect/Predicate"

assert.deepStrictEqual(isError(new Error()), true)

assert.deepStrictEqual(isError(null), false)
assert.deepStrictEqual(isError({}), false)

Added in v2.0.0

isFunction

Tests if a value is a function.

Signature

export declare const isFunction: (input: unknown) => input is Function

Example

import { isFunction } from "effect/Predicate"

assert.deepStrictEqual(isFunction(isFunction), true)

assert.deepStrictEqual(isFunction("function"), false)

Added in v2.0.0

isIterable

A guard that succeeds when the input is an Iterable.

Signature

export declare const isIterable: (input: unknown) => input is Iterable<unknown>

Example

import { isIterable } from "effect/Predicate"

assert.deepStrictEqual(isIterable([]), true)
assert.deepStrictEqual(isIterable(new Set()), true)

assert.deepStrictEqual(isIterable(null), false)
assert.deepStrictEqual(isIterable({}), false)

Added in v2.0.0

isMap

Tests if a value is a Map.

Signature

export declare const isMap: (input: unknown) => input is Map<unknown, unknown>

Example

import { isMap } from "effect/Predicate"

assert.deepStrictEqual(isMap(new Map()), true)
assert.deepStrictEqual(isMap({}), false)
assert.deepStrictEqual(isMap(null), false)
assert.deepStrictEqual(isMap(undefined), false)

Added in v2.0.0

isNever

A guard that always fails.

Signature

export declare const isNever: (input: unknown) => input is never

Example

import { isNever } from "effect/Predicate"

assert.deepStrictEqual(isNever(null), false)
assert.deepStrictEqual(isNever(undefined), false)
assert.deepStrictEqual(isNever({}), false)
assert.deepStrictEqual(isNever([]), false)

Added in v2.0.0

isNotNull

Tests if a value is not null.

Signature

export declare const isNotNull: <A>(input: A) => input is Exclude<A, null>

Example

import { isNotNull } from "effect/Predicate"

assert.deepStrictEqual(isNotNull(undefined), true)
assert.deepStrictEqual(isNotNull("null"), true)

assert.deepStrictEqual(isNotNull(null), false)

Added in v2.0.0

isNotNullable

A guard that succeeds when the input is not null or undefined.

Signature

export declare const isNotNullable: <A>(input: A) => input is NonNullable<A>

Example

import { isNotNullable } from "effect/Predicate"

assert.deepStrictEqual(isNotNullable({}), true)
assert.deepStrictEqual(isNotNullable([]), true)

assert.deepStrictEqual(isNotNullable(null), false)
assert.deepStrictEqual(isNotNullable(undefined), false)

Added in v2.0.0

isNotUndefined

Tests if a value is not undefined.

Signature

export declare const isNotUndefined: <A>(input: A) => input is Exclude<A, undefined>

Example

import { isNotUndefined } from "effect/Predicate"

assert.deepStrictEqual(isNotUndefined(null), true)
assert.deepStrictEqual(isNotUndefined("undefined"), true)

assert.deepStrictEqual(isNotUndefined(undefined), false)

Added in v2.0.0

isNull

Tests if a value is null.

Signature

export declare const isNull: (input: unknown) => input is null

Example

import { isNull } from "effect/Predicate"

assert.deepStrictEqual(isNull(null), true)

assert.deepStrictEqual(isNull(undefined), false)
assert.deepStrictEqual(isNull("null"), false)

Added in v2.0.0

isNullable

A guard that succeeds when the input is null or undefined.

Signature

export declare const isNullable: <A>(input: A) => input is Extract<A, null | undefined>

Example

import { isNullable } from "effect/Predicate"

assert.deepStrictEqual(isNullable(null), true)
assert.deepStrictEqual(isNullable(undefined), true)

assert.deepStrictEqual(isNullable({}), false)
assert.deepStrictEqual(isNullable([]), false)

Added in v2.0.0

isNumber

Tests if a value is a number.

Signature

export declare const isNumber: (input: unknown) => input is number

Example

import { isNumber } from "effect/Predicate"

assert.deepStrictEqual(isNumber(2), true)

assert.deepStrictEqual(isNumber("2"), false)

Added in v2.0.0

isObject

Tests if a value is an object.

Signature

export declare const isObject: (input: unknown) => input is object

Example

import { isObject } from "effect/Predicate"

assert.deepStrictEqual(isObject({}), true)
assert.deepStrictEqual(isObject([]), true)

assert.deepStrictEqual(isObject(null), false)
assert.deepStrictEqual(isObject(undefined), false)

Added in v2.0.0

isPromise

A guard that succeeds when the input is a Promise.

Signature

export declare const isPromise: (input: unknown) => input is Promise<unknown>

Example

import { isPromise } from "effect/Predicate"

assert.deepStrictEqual(isPromise({}), false)
assert.deepStrictEqual(isPromise(Promise.resolve("hello")), true)

Added in v2.0.0

isPromiseLike

Signature

export declare const isPromiseLike: (input: unknown) => input is PromiseLike<unknown>

Added in v2.0.0

isReadonlyRecord

A guard that succeeds when the input is a readonly record.

Signature

export declare const isReadonlyRecord: (
  input: unknown
) => input is { readonly [x: string]: unknown; readonly [x: symbol]: unknown }

Example

import { isReadonlyRecord } from "effect/Predicate"

assert.deepStrictEqual(isReadonlyRecord({}), true)
assert.deepStrictEqual(isReadonlyRecord({ a: 1 }), true)

assert.deepStrictEqual(isReadonlyRecord([]), false)
assert.deepStrictEqual(isReadonlyRecord([1, 2, 3]), false)
assert.deepStrictEqual(isReadonlyRecord(null), false)
assert.deepStrictEqual(isReadonlyRecord(undefined), false)

Added in v2.0.0

isRecord

A guard that succeeds when the input is a record.

Signature

export declare const isRecord: (input: unknown) => input is { [x: string]: unknown; [x: symbol]: unknown }

Example

import { isRecord } from "effect/Predicate"

assert.deepStrictEqual(isRecord({}), true)
assert.deepStrictEqual(isRecord({ a: 1 }), true)

assert.deepStrictEqual(isRecord([]), false)
assert.deepStrictEqual(isRecord([1, 2, 3]), false)
assert.deepStrictEqual(isRecord(null), false)
assert.deepStrictEqual(isRecord(undefined), false)
assert.deepStrictEqual(
  isRecord(() => null),
  false
)

Added in v2.0.0

isSet

Tests if a value is a Set.

Signature

export declare const isSet: (input: unknown) => input is Set<unknown>

Example

import { isSet } from "effect/Predicate"

assert.deepStrictEqual(isSet(new Set([1, 2])), true)
assert.deepStrictEqual(isSet(new Set()), true)
assert.deepStrictEqual(isSet({}), false)
assert.deepStrictEqual(isSet(null), false)
assert.deepStrictEqual(isSet(undefined), false)

Added in v2.0.0

isString

Tests if a value is a string.

Signature

export declare const isString: (input: unknown) => input is string

Example

import { isString } from "effect/Predicate"

assert.deepStrictEqual(isString("a"), true)

assert.deepStrictEqual(isString(1), false)

Added in v2.0.0

isSymbol

Tests if a value is a symbol.

Signature

export declare const isSymbol: (input: unknown) => input is symbol

Example

import { isSymbol } from "effect/Predicate"

assert.deepStrictEqual(isSymbol(Symbol.for("a")), true)

assert.deepStrictEqual(isSymbol("a"), false)

Added in v2.0.0

isTagged

Tests if a value is an object with a property _tag that matches the given tag.

Signature

export declare const isTagged: {
  <K extends string>(tag: K): (self: unknown) => self is { _tag: K }
  <K extends string>(self: unknown, tag: K): self is { _tag: K }
}

Example

import { isTagged } from "effect/Predicate"

assert.deepStrictEqual(isTagged(1, "a"), false)
assert.deepStrictEqual(isTagged(null, "a"), false)
assert.deepStrictEqual(isTagged({}, "a"), false)
assert.deepStrictEqual(isTagged({ a: "a" }, "a"), false)
assert.deepStrictEqual(isTagged({ _tag: "a" }, "a"), true)
assert.deepStrictEqual(isTagged("a")({ _tag: "a" }), true)

Added in v2.0.0

isTruthy

Tests if a value is truthy.

Signature

export declare const isTruthy: (input: unknown) => boolean

Example

import { isTruthy } from "effect/Predicate"

assert.deepStrictEqual(isTruthy(1), true)
assert.deepStrictEqual(isTruthy(0), false)
assert.deepStrictEqual(isTruthy(""), false)

Added in v2.0.0

isUint8Array

A guard that succeeds when the input is a Uint8Array.

Signature

export declare const isUint8Array: (input: unknown) => input is Uint8Array

Example

import { isUint8Array } from "effect/Predicate"

assert.deepStrictEqual(isUint8Array(new Uint8Array()), true)

assert.deepStrictEqual(isUint8Array(null), false)
assert.deepStrictEqual(isUint8Array({}), false)

Added in v2.0.0

isUndefined

Tests if a value is undefined.

Signature

export declare const isUndefined: (input: unknown) => input is undefined

Example

import { isUndefined } from "effect/Predicate"

assert.deepStrictEqual(isUndefined(undefined), true)

assert.deepStrictEqual(isUndefined(null), false)
assert.deepStrictEqual(isUndefined("undefined"), false)

Added in v2.0.0

isUnknown

A guard that always succeeds.

Signature

export declare const isUnknown: (input: unknown) => input is unknown

Example

import { isUnknown } from "effect/Predicate"

assert.deepStrictEqual(isUnknown(null), true)
assert.deepStrictEqual(isUnknown(undefined), true)

assert.deepStrictEqual(isUnknown({}), true)
assert.deepStrictEqual(isUnknown([]), true)

Added in v2.0.0

models

Predicate (interface)

Signature

export interface Predicate<in A> {
  (a: A): boolean
}

Added in v2.0.0

Refinement (interface)

Signature

export interface Refinement<in A, out B extends A> {
  (a: A): a is B
}

Added in v2.0.0

type lambdas

PredicateTypeLambda (interface)

Signature

export interface PredicateTypeLambda extends TypeLambda {
  readonly type: Predicate<this["Target"]>
}

Added in v2.0.0

utils

compose

Signature

export declare const compose: {
  <A, B extends A, C extends B>(bc: Refinement<B, C>): (ab: Refinement<A, B>) => Refinement<A, C>
  <A, B extends A, C extends B>(ab: Refinement<A, B>, bc: Refinement<B, C>): Refinement<A, C>
}

Added in v2.0.0

struct

Signature

export declare const struct: <R extends Record<string, Predicate<any>>>(
  fields: R
) => Predicate<{ readonly [K in keyof R]: [R[K]] extends [Predicate<infer A>] ? A : never }>

Added in v2.0.0

tuple

Similar to Promise.all but operates on Predicates.

[Predicate<A>, Predicate<B>, ...] -> Predicate<[A, B, ...]>

Signature

export declare const tuple: <T extends readonly Predicate<any>[]>(
  ...elements: T
) => Predicate<Readonly<{ [I in keyof T]: [T[I]] extends [Predicate<infer A>] ? A : never }>>

Added in v2.0.0