<A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (
self: Iterable<A>
) => Array<A>
<A, B, X>(
self: Iterable<A>,
f: (input: A, i: number) => Result.Result<B, X>
): Array<A>Drops elements from the start while a Filter succeeds.
When to use
Use when you need to drop a prefix from an iterable by computing a Result
per element instead of using a simple boolean predicate.
Details
The filter receives (element, index). The result contains the remaining
original elements after the first filter failure.
export const const dropWhileFilter: {
<A, B, X>(
f: (
input: NoInfer<A>,
i: number
) => Result.Result<B, X>
): (self: Iterable<A>) => Array<A>
<A, B, X>(
self: Iterable<A>,
f: (
input: A,
i: number
) => Result.Result<B, X>
): Array<A>
}
Drops elements from the start while a Filter succeeds.
When to use
Use when you need to drop a prefix from an iterable by computing a Result
per element instead of using a simple boolean predicate.
Details
The filter receives (element, index). The result contains the remaining
original elements after the first filter failure.
dropWhileFilter: {
<function (type parameter) A in <A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<A>A, function (type parameter) B in <A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<A>B, function (type parameter) X in <A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<A>X>(f: (
input: NoInfer<A>,
i: number
) => Result.Result<B, X>
input: NoInfer<A>input: 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, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<A>A>, i: numberi: number) => import ResultResult.type Result<A, E = never> = Result.Success<A, E> | Result.Failure<A, E>A value that is either Success<A, E> or Failure<A, E>.
When to use
Use when both success and failure should remain available as data and
Option would lose failure information.
Details
- Use
succeed
/
fail
to construct
- Use
match
to fold both branches
- Use
isSuccess
/
isFailure
to narrow the type
E defaults to never, so Result<number> means a result that cannot fail.
Example (Creating and matching a Result)
import { Result } from "effect"
const success = Result.succeed(42)
const failure = Result.fail("something went wrong")
const message = Result.match(success, {
onSuccess: (value) => `Success: ${value}`,
onFailure: (error) => `Error: ${error}`
})
console.log(message)
// Output: "Success: 42"
Namespace containing type-level utilities for extracting the inner types
of a Result.
Example (Extracting inner types)
import type { Result } from "effect"
type R = Result.Result<number, string>
// number
type A = Result.Result.Success<R>
// string
type E = Result.Result.Failure<R>
Result<function (type parameter) B in <A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<A>B, function (type parameter) X in <A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<A>X>): (self: Iterable<A>self: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) A in <A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<A>A>) => interface Array<T>Array<function (type parameter) A in <A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<A>A>
<function (type parameter) A in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>A, function (type parameter) B in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>B, function (type parameter) X in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>X>(self: Iterable<A>self: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) A in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>A>, f: (
input: A,
i: number
) => Result.Result<B, X>
input: Ainput: function (type parameter) A in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>A, i: numberi: number) => import ResultResult.type Result<A, E = never> = Result.Success<A, E> | Result.Failure<A, E>A value that is either Success<A, E> or Failure<A, E>.
When to use
Use when both success and failure should remain available as data and
Option would lose failure information.
Details
- Use
succeed
/
fail
to construct
- Use
match
to fold both branches
- Use
isSuccess
/
isFailure
to narrow the type
E defaults to never, so Result<number> means a result that cannot fail.
Example (Creating and matching a Result)
import { Result } from "effect"
const success = Result.succeed(42)
const failure = Result.fail("something went wrong")
const message = Result.match(success, {
onSuccess: (value) => `Success: ${value}`,
onFailure: (error) => `Error: ${error}`
})
console.log(message)
// Output: "Success: 42"
Namespace containing type-level utilities for extracting the inner types
of a Result.
Example (Extracting inner types)
import type { Result } from "effect"
type R = Result.Result<number, string>
// number
type A = Result.Result.Success<R>
// string
type E = Result.Result.Failure<R>
Result<function (type parameter) B in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>B, function (type parameter) X in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>X>): interface Array<T>Array<function (type parameter) A in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>A>
} = dual<(...args: Array<any>) => any, <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>) => Array<A>>(arity: 2, body: <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>) => Array<A>): ((...args: Array<any>) => any) & (<A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>) => 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, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>A, function (type parameter) B in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>B, function (type parameter) X in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>X>(self: Iterable<A>self: interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) A in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>A>, f: (
input: A,
i: number
) => Result.Result<B, X>
input: Ainput: function (type parameter) A in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>A, i: numberi: number) => import ResultResult.type Result<A, E = never> = Result.Success<A, E> | Result.Failure<A, E>A value that is either Success<A, E> or Failure<A, E>.
When to use
Use when both success and failure should remain available as data and
Option would lose failure information.
Details
- Use
succeed
/
fail
to construct
- Use
match
to fold both branches
- Use
isSuccess
/
isFailure
to narrow the type
E defaults to never, so Result<number> means a result that cannot fail.
Example (Creating and matching a Result)
import { Result } from "effect"
const success = Result.succeed(42)
const failure = Result.fail("something went wrong")
const message = Result.match(success, {
onSuccess: (value) => `Success: ${value}`,
onFailure: (error) => `Error: ${error}`
})
console.log(message)
// Output: "Success: 42"
Namespace containing type-level utilities for extracting the inner types
of a Result.
Example (Extracting inner types)
import type { Result } from "effect"
type R = Result.Result<number, string>
// number
type A = Result.Result.Success<R>
// string
type E = Result.Result.Failure<R>
Result<function (type parameter) B in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>B, function (type parameter) X in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>X>): interface Array<T>Array<function (type parameter) A in <A, B, X>(self: Iterable<A>, f: (input: A, i: number) => Result.Result<B, X>): Array<A>A> => {
const const input: A[]input = const fromIterable: <A>(
collection: Iterable<A>
) => A[]
Converts an Iterable to an Array.
When to use
Use to convert any Iterable (Set, Generator, etc.) into an array.
Details
If the input is already an array, this returns it by reference without
copying. Otherwise, it creates a new array from the iterable. Use copy if
you need a fresh array even when the input is already an array.
Example (Converting a Set to an array)
import { Array } from "effect"
const result = Array.fromIterable(new Set([1, 2, 3]))
console.log(result) // [1, 2, 3]
fromIterable(self: Iterable<A>self)
let let i: numberi = 0
while (let i: numberi < const input: A[]input.Array<T>.length: numberGets or sets the length of the array. This is a number one higher than the highest index in the array.
length) {
if (import ResultResult.const isFailure: <A, E>(
self: Result<A, E>
) => self is Failure<A, E>
Checks whether a Result is a Failure.
When to use
Use to narrow a known Result to the Failure variant.
Details
- Acts as a TypeScript type guard, narrowing to
Failure<A, E>
- After narrowing, you can access
.failure to read the error value
Example (Narrowing to failure)
import { Result } from "effect"
const result = Result.fail("oops")
if (Result.isFailure(result)) {
console.log(result.failure)
// Output: "oops"
}
isFailure(f: (
input: A,
i: number
) => Result.Result<B, X>
const input: A[]input[let i: numberi], let i: numberi))) {
break
}
let i: numberi++
}
return const input: A[]input.Array<A>.slice(start?: number, end?: number): A[]Returns a copy of a section of an array.
For both start and end, a negative index can be used to indicate an offset from the end of the array.
For example, -2 refers to the second to last element of the array.
slice(let i: numberi)
}
)