<Fail, Fail2>(f: (fail: Fail) => Fail2): <Input, Pass>(
self: Filter<Input, Pass, Fail>
) => Filter<Input, Pass, Fail2>
<Input, Pass, Fail, Fail2>(
self: Filter<Input, Pass, Fail>,
f: (fail: Fail) => Fail2
): Filter<Input, Pass, Fail2>Transforms the failure value produced by a Filter, leaving successful
results unchanged.
export const const mapFail: {
<Fail, Fail2>(f: (fail: Fail) => Fail2): <
Input,
Pass
>(
self: Filter<Input, Pass, Fail>
) => Filter<Input, Pass, Fail2>
<Input, Pass, Fail, Fail2>(
self: Filter<Input, Pass, Fail>,
f: (fail: Fail) => Fail2
): Filter<Input, Pass, Fail2>
}
Transforms the failure value produced by a Filter, leaving successful
results unchanged.
mapFail: {
<function (type parameter) Fail in <Fail, Fail2>(f: (fail: Fail) => Fail2): <Input, Pass>(self: Filter<Input, Pass, Fail>) => Filter<Input, Pass, Fail2>Fail, function (type parameter) Fail2 in <Fail, Fail2>(f: (fail: Fail) => Fail2): <Input, Pass>(self: Filter<Input, Pass, Fail>) => Filter<Input, Pass, Fail2>Fail2>(f: (fail: Fail) => Fail2f: (fail: Failfail: function (type parameter) Fail in <Fail, Fail2>(f: (fail: Fail) => Fail2): <Input, Pass>(self: Filter<Input, Pass, Fail>) => Filter<Input, Pass, Fail2>Fail) => function (type parameter) Fail2 in <Fail, Fail2>(f: (fail: Fail) => Fail2): <Input, Pass>(self: Filter<Input, Pass, Fail>) => Filter<Input, Pass, Fail2>Fail2): <function (type parameter) Input in <Input, Pass>(self: Filter<Input, Pass, Fail>): Filter<Input, Pass, Fail2>Input, function (type parameter) Pass in <Input, Pass>(self: Filter<Input, Pass, Fail>): Filter<Input, Pass, Fail2>Pass>(self: Filter<Input, Pass, Fail>self: interface Filter<in Input, out Pass = Input, out Fail = Input>Represents a filter function that can transform inputs to outputs or filter them out.
Details
A filter takes an input value and either returns a boxed pass value or the
special fail type to indicate the value should be filtered out.
Example (Defining a positive number filter)
import { Filter, Result } from "effect"
// A filter that only passes positive numbers
const positiveFilter: Filter.Filter<number> = (n) => n > 0 ? Result.succeed(n) : Result.fail(n)
console.log(positiveFilter(5)) // Result.succeed(5)
console.log(positiveFilter(-3)) // Result.fail(-3)
Filter<function (type parameter) Input in <Input, Pass>(self: Filter<Input, Pass, Fail>): Filter<Input, Pass, Fail2>Input, function (type parameter) Pass in <Input, Pass>(self: Filter<Input, Pass, Fail>): Filter<Input, Pass, Fail2>Pass, function (type parameter) Fail in <Fail, Fail2>(f: (fail: Fail) => Fail2): <Input, Pass>(self: Filter<Input, Pass, Fail>) => Filter<Input, Pass, Fail2>Fail>) => interface Filter<in Input, out Pass = Input, out Fail = Input>Represents a filter function that can transform inputs to outputs or filter them out.
Details
A filter takes an input value and either returns a boxed pass value or the
special fail type to indicate the value should be filtered out.
Example (Defining a positive number filter)
import { Filter, Result } from "effect"
// A filter that only passes positive numbers
const positiveFilter: Filter.Filter<number> = (n) => n > 0 ? Result.succeed(n) : Result.fail(n)
console.log(positiveFilter(5)) // Result.succeed(5)
console.log(positiveFilter(-3)) // Result.fail(-3)
Filter<function (type parameter) Input in <Input, Pass>(self: Filter<Input, Pass, Fail>): Filter<Input, Pass, Fail2>Input, function (type parameter) Pass in <Input, Pass>(self: Filter<Input, Pass, Fail>): Filter<Input, Pass, Fail2>Pass, function (type parameter) Fail2 in <Fail, Fail2>(f: (fail: Fail) => Fail2): <Input, Pass>(self: Filter<Input, Pass, Fail>) => Filter<Input, Pass, Fail2>Fail2>
<function (type parameter) Input in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (fail: Fail) => Fail2): Filter<Input, Pass, Fail2>Input, function (type parameter) Pass in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (fail: Fail) => Fail2): Filter<Input, Pass, Fail2>Pass, function (type parameter) Fail in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (fail: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail, function (type parameter) Fail2 in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (fail: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail2>(
self: Filter<Input, Pass, Fail>self: interface Filter<in Input, out Pass = Input, out Fail = Input>Represents a filter function that can transform inputs to outputs or filter them out.
Details
A filter takes an input value and either returns a boxed pass value or the
special fail type to indicate the value should be filtered out.
Example (Defining a positive number filter)
import { Filter, Result } from "effect"
// A filter that only passes positive numbers
const positiveFilter: Filter.Filter<number> = (n) => n > 0 ? Result.succeed(n) : Result.fail(n)
console.log(positiveFilter(5)) // Result.succeed(5)
console.log(positiveFilter(-3)) // Result.fail(-3)
Filter<function (type parameter) Input in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (fail: Fail) => Fail2): Filter<Input, Pass, Fail2>Input, function (type parameter) Pass in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (fail: Fail) => Fail2): Filter<Input, Pass, Fail2>Pass, function (type parameter) Fail in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (fail: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail>,
f: (fail: Fail) => Fail2f: (fail: Failfail: function (type parameter) Fail in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (fail: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail) => function (type parameter) Fail2 in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (fail: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail2
): interface Filter<in Input, out Pass = Input, out Fail = Input>Represents a filter function that can transform inputs to outputs or filter them out.
Details
A filter takes an input value and either returns a boxed pass value or the
special fail type to indicate the value should be filtered out.
Example (Defining a positive number filter)
import { Filter, Result } from "effect"
// A filter that only passes positive numbers
const positiveFilter: Filter.Filter<number> = (n) => n > 0 ? Result.succeed(n) : Result.fail(n)
console.log(positiveFilter(5)) // Result.succeed(5)
console.log(positiveFilter(-3)) // Result.fail(-3)
Filter<function (type parameter) Input in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (fail: Fail) => Fail2): Filter<Input, Pass, Fail2>Input, function (type parameter) Pass in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (fail: Fail) => Fail2): Filter<Input, Pass, Fail2>Pass, function (type parameter) Fail2 in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (fail: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail2>
} = dual<(...args: Array<any>) => any, <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2) => Filter<Input, Pass, Fail2>>(arity: 2, body: <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2) => Filter<Input, Pass, Fail2>): ((...args: Array<any>) => any) & (<Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2) => Filter<Input, Pass, Fail2>) (+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) Input in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Input, function (type parameter) Pass in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Pass, function (type parameter) Fail in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail, function (type parameter) Fail2 in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail2>(
self: Filter<Input, Pass, Fail>self: interface Filter<in Input, out Pass = Input, out Fail = Input>Represents a filter function that can transform inputs to outputs or filter them out.
Details
A filter takes an input value and either returns a boxed pass value or the
special fail type to indicate the value should be filtered out.
Example (Defining a positive number filter)
import { Filter, Result } from "effect"
// A filter that only passes positive numbers
const positiveFilter: Filter.Filter<number> = (n) => n > 0 ? Result.succeed(n) : Result.fail(n)
console.log(positiveFilter(5)) // Result.succeed(5)
console.log(positiveFilter(-3)) // Result.fail(-3)
Filter<function (type parameter) Input in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Input, function (type parameter) Pass in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Pass, function (type parameter) Fail in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail>,
f: (value: Fail) => Fail2f: (value: Failvalue: function (type parameter) Fail in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail) => function (type parameter) Fail2 in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail2
): interface Filter<in Input, out Pass = Input, out Fail = Input>Represents a filter function that can transform inputs to outputs or filter them out.
Details
A filter takes an input value and either returns a boxed pass value or the
special fail type to indicate the value should be filtered out.
Example (Defining a positive number filter)
import { Filter, Result } from "effect"
// A filter that only passes positive numbers
const positiveFilter: Filter.Filter<number> = (n) => n > 0 ? Result.succeed(n) : Result.fail(n)
console.log(positiveFilter(5)) // Result.succeed(5)
console.log(positiveFilter(-3)) // Result.fail(-3)
Filter<function (type parameter) Input in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Input, function (type parameter) Pass in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Pass, function (type parameter) Fail2 in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail2> =>
(input: Inputinput: function (type parameter) Input in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Input): 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) Pass in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Pass, function (type parameter) Fail2 in <Input, Pass, Fail, Fail2>(self: Filter<Input, Pass, Fail>, f: (value: Fail) => Fail2): Filter<Input, Pass, Fail2>Fail2> => import ResultResult.const mapError: {
<E, E2>(f: (err: E) => E2): <A>(
self: Result<A, E>
) => Result<A, E2>
<A, E, E2>(
self: Result<A, E>,
f: (err: E) => E2
): Result<A, E2>
}
self: Filter<Input, Pass, Fail>self(input: Inputinput), f: (value: Fail) => Fail2f))