<A, B extends A>(refinement: (a: NoInfer<A>, i: number) => a is B): (
self: Iterable<A>
) => Array<B>
<A>(predicate: (a: NoInfer<A>, i: number) => boolean): (
self: Iterable<A>
) => Array<A>
<A, B extends A>(
self: Iterable<A>,
refinement: (a: A, i: number) => a is B
): Array<B>
<A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A>Takes elements from the start while the predicate holds, stopping at the first element that fails.
When to use
Use to keep the leading elements of an iterable while each element satisfies a predicate, returning the retained prefix as an array.
Details
Supports refinements for type narrowing. The predicate receives
(element, index).
Example (Taking while condition holds)
import { Array } from "effect"
console.log(Array.takeWhile([1, 3, 2, 4, 1, 2], (x) => x < 4)) // [1, 3, 2]export const const takeWhile: {
<A, B extends A>(
refinement: (
a: NoInfer<A>,
i: number
) => a is B
): (self: Iterable<A>) => Array<B>
<A>(
predicate: (
a: NoInfer<A>,
i: number
) => boolean
): (self: Iterable<A>) => Array<A>
<A, B extends A>(
self: Iterable<A>,
refinement: (a: A, i: number) => a is B
): Array<B>
<A>(
self: Iterable<A>,
predicate: (a: A, i: number) => boolean
): Array<A>
}
Takes elements from the start while the predicate holds, stopping at the
first element that fails.
When to use
Use to keep the leading elements of an iterable while each element satisfies
a predicate, returning the retained prefix as an array.
Details
Supports refinements for type narrowing. The predicate receives
(element, index).
Example (Taking while condition holds)
import { Array } from "effect"
console.log(Array.takeWhile([1, 3, 2, 4, 1, 2], (x) => x < 4)) // [1, 3, 2]
takeWhile: {
<function (type parameter) A in <A, B extends A>(refinement: (a: NoInfer<A>, i: number) => a is B): (self: Iterable<A>) => Array<B>A, function (type parameter) B in <A, B extends A>(refinement: (a: NoInfer<A>, i: number) => a is B): (self: Iterable<A>) => Array<B>B extends function (type parameter) A in <A, B extends A>(refinement: (a: NoInfer<A>, i: number) => a is B): (self: Iterable<A>) => Array<B>A>(refinement: (a: NoInfer<A>, i: number) => a is Brefinement: (a: NoInfer<A>a: type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) A in <A, B extends A>(refinement: (a: NoInfer<A>, i: number) => a is B): (self: Iterable<A>) => Array<B>A>, i: numberi: number) => a: NoInfer<A>a is function (type parameter) B in <A, B extends A>(refinement: (a: NoInfer<A>, i: number) => a is B): (self: Iterable<A>) => Array<B>B): (self: Iterable<A>self: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) A in <A, B extends A>(refinement: (a: NoInfer<A>, i: number) => a is B): (self: Iterable<A>) => Array<B>A>) => interface Array<T>Array<function (type parameter) B in <A, B extends A>(refinement: (a: NoInfer<A>, i: number) => a is B): (self: Iterable<A>) => Array<B>B>
<function (type parameter) A in <A>(predicate: (a: NoInfer<A>, i: number) => boolean): (self: Iterable<A>) => Array<A>A>(predicate: (a: NoInfer<A>, i: number) => booleanpredicate: (a: NoInfer<A>a: type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) A in <A>(predicate: (a: NoInfer<A>, i: number) => boolean): (self: Iterable<A>) => Array<A>A>, i: numberi: number) => boolean): (self: Iterable<A>self: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) A in <A>(predicate: (a: NoInfer<A>, i: number) => boolean): (self: Iterable<A>) => Array<A>A>) => interface Array<T>Array<function (type parameter) A in <A>(predicate: (a: NoInfer<A>, i: number) => boolean): (self: Iterable<A>) => Array<A>A>
<function (type parameter) A in <A, B extends A>(self: Iterable<A>, refinement: (a: A, i: number) => a is B): Array<B>A, function (type parameter) B in <A, B extends A>(self: Iterable<A>, refinement: (a: A, i: number) => a is B): Array<B>B extends function (type parameter) A in <A, B extends A>(self: Iterable<A>, refinement: (a: A, i: number) => a is B): Array<B>A>(self: Iterable<A>self: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) A in <A, B extends A>(self: Iterable<A>, refinement: (a: A, i: number) => a is B): Array<B>A>, refinement: (a: A, i: number) => a is Brefinement: (a: Aa: function (type parameter) A in <A, B extends A>(self: Iterable<A>, refinement: (a: A, i: number) => a is B): Array<B>A, i: numberi: number) => a: Aa is function (type parameter) B in <A, B extends A>(self: Iterable<A>, refinement: (a: A, i: number) => a is B): Array<B>B): interface Array<T>Array<function (type parameter) B in <A, B extends A>(self: Iterable<A>, refinement: (a: A, i: number) => a is B): Array<B>B>
<function (type parameter) A in <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A>A>(self: Iterable<A>self: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) A in <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A>A>, predicate: (a: A, i: number) => booleanpredicate: (a: Aa: function (type parameter) A in <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A>A, i: numberi: number) => boolean): interface Array<T>Array<function (type parameter) A in <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A>A>
} = dual<(...args: Array<any>) => any, <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean) => Array<A>>(arity: 2, body: <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean) => Array<A>): ((...args: Array<any>) => any) & (<A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean) => Array<A>) (+1 overload)Creates a function that can be called in data-first style or data-last
(pipe-friendly) style.
When to use
Use to expose one implementation through both direct and pipe-friendly
call styles.
Details
Pass either the arity of the uncurried function or a predicate that decides
whether the current call is data-first. Arity is the common case. Use a
predicate when optional arguments make arity ambiguous.
Example (Selecting data-first or data-last style by arity)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(2, (self, that) => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Defining overloads with call signatures)
import { Function, pipe } from "effect"
const sum: {
(that: number): (self: number) => number
(self: number, that: number): number
} = Function.dual(2, (self: number, that: number): number => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Selecting data-first or data-last style with a predicate)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(
(args) => args.length === 2,
(self, that) => self + that
)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
dual(2, <function (type parameter) A in <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A>A>(self: Iterable<A>self: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) A in <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A>A>, predicate: (a: A, i: number) => booleanpredicate: (a: Aa: function (type parameter) A in <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A>A, i: numberi: number) => boolean): interface Array<T>Array<function (type parameter) A in <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A>A> => {
let let i: numberi = 0
const const out: A[]out: interface Array<T>Array<function (type parameter) A in <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A>A> = []
for (const const a: Aa of self: Iterable<A>self) {
if (!predicate: (a: A, i: number) => booleanpredicate(const a: Aa, let i: numberi)) {
break
}
const out: A[]out.Array<A>.push(...items: A[]): numberAppends new elements to the end of an array, and returns the new length of the array.
push(const a: Aa)
let i: numberi++
}
return const out: A[]out
})