<PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <
InputL,
FailL
>(
left: Filter<InputL, PassL, FailL>
) => Filter<InputL, PassR, FailL | FailR>
<InputL, PassL, FailL, PassR, FailR>(
left: Filter<InputL, PassL, FailL>,
right: Filter<PassL, PassR, FailR>
): Filter<InputL, PassR, FailL | FailR>Composes two filters sequentially, feeding the output of the first into the second.
Example (Composing filters)
import { Filter, Result } from "effect"
const stringFilter = Filter.string
const nonEmptyUpper = Filter.make((s: string) =>
s.length > 0 ? Result.succeed(s.toUpperCase()) : Result.fail(s)
)
const stringToUpper = Filter.compose(stringFilter, nonEmptyUpper)combinators
Source effect/Filter.ts:73317 lines
export const const compose: {
<PassL, PassR, FailR>(
right: Filter<PassL, PassR, FailR>
): <InputL, FailL>(
left: Filter<InputL, PassL, FailL>
) => Filter<InputL, PassR, FailL | FailR>
<InputL, PassL, FailL, PassR, FailR>(
left: Filter<InputL, PassL, FailL>,
right: Filter<PassL, PassR, FailR>
): Filter<InputL, PassR, FailL | FailR>
}
Composes two filters sequentially, feeding the output of the first into the second.
Example (Composing filters)
import { Filter, Result } from "effect"
const stringFilter = Filter.string
const nonEmptyUpper = Filter.make((s: string) =>
s.length > 0 ? Result.succeed(s.toUpperCase()) : Result.fail(s)
)
const stringToUpper = Filter.compose(stringFilter, nonEmptyUpper)
compose: {
<function (type parameter) PassL in <PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <InputL, FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, FailL | FailR>PassL, function (type parameter) PassR in <PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <InputL, FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, FailL | FailR>PassR, function (type parameter) FailR in <PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <InputL, FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, FailL | FailR>FailR>(
right: Filter<PassL, PassR, FailR>right: 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) PassL in <PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <InputL, FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, FailL | FailR>PassL, function (type parameter) PassR in <PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <InputL, FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, FailL | FailR>PassR, function (type parameter) FailR in <PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <InputL, FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, FailL | FailR>FailR>
): <function (type parameter) InputL in <InputL, FailL>(left: Filter<InputL, PassL, FailL>): Filter<InputL, PassR, FailL | FailR>InputL, function (type parameter) FailL in <InputL, FailL>(left: Filter<InputL, PassL, FailL>): Filter<InputL, PassR, FailL | FailR>FailL>(left: Filter<InputL, PassL, FailL>left: 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) InputL in <InputL, FailL>(left: Filter<InputL, PassL, FailL>): Filter<InputL, PassR, FailL | FailR>InputL, function (type parameter) PassL in <PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <InputL, FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, FailL | FailR>PassL, function (type parameter) FailL in <InputL, FailL>(left: Filter<InputL, PassL, FailL>): Filter<InputL, PassR, FailL | FailR>FailL>) => 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) InputL in <InputL, FailL>(left: Filter<InputL, PassL, FailL>): Filter<InputL, PassR, FailL | FailR>InputL, function (type parameter) PassR in <PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <InputL, FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, FailL | FailR>PassR, function (type parameter) FailL in <InputL, FailL>(left: Filter<InputL, PassL, FailL>): Filter<InputL, PassR, FailL | FailR>FailL | function (type parameter) FailR in <PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <InputL, FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, FailL | FailR>FailR>
<function (type parameter) InputL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>InputL, function (type parameter) PassL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>PassL, function (type parameter) FailL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailL, function (type parameter) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>PassR, function (type parameter) FailR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailR>(
left: Filter<InputL, PassL, FailL>left: 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) InputL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>InputL, function (type parameter) PassL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>PassL, function (type parameter) FailL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailL>,
right: Filter<PassL, PassR, FailR>right: 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) PassL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>PassL, function (type parameter) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>PassR, function (type parameter) FailR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailR>
): 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) InputL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>InputL, function (type parameter) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>PassR, function (type parameter) FailL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailL | function (type parameter) FailR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailR>
} = dual<(...args: Array<any>) => any, <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>) => Filter<InputL, PassR, FailL | FailR>>(arity: 2, body: <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>) => Filter<InputL, PassR, FailL | FailR>): ((...args: Array<any>) => any) & (<InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>) => Filter<InputL, PassR, FailL | FailR>) (+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) InputL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>InputL, function (type parameter) PassL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>PassL, function (type parameter) FailL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailL, function (type parameter) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>PassR, function (type parameter) FailR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailR>(
left: Filter<InputL, PassL, FailL>left: 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) InputL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>InputL, function (type parameter) PassL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>PassL, function (type parameter) FailL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailL>,
right: Filter<PassL, PassR, FailR>right: 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) PassL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>PassL, function (type parameter) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>PassR, function (type parameter) FailR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailR>
): 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) InputL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>InputL, function (type parameter) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>PassR, function (type parameter) FailL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailL | function (type parameter) FailR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailR> =>
(input: InputLinput) => {
const const leftOut: Result.Result<PassL, FailL>leftOut = left: Filter<InputL, PassL, FailL>left(input: InputLinput)
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(const leftOut: Result.Result<PassL, FailL>leftOut)) return const leftOut: Result.Failure<
PassL,
FailL
>
const leftOut: {
_tag: "Failure";
_op: "Failure";
failure: E;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
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<never, function (type parameter) FailL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailL | function (type parameter) FailR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, FailL | FailR>FailR>
return right: Filter<PassL, PassR, FailR>right(const leftOut: Result.Success<
PassL,
FailL
>
const leftOut: {
_tag: "Success";
_op: "Success";
success: A;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
Success<PassL, FailL>.success: PassLsuccess)
})