<InputL, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <
FailL
>(
left: Filter<InputL, PassL, FailL>
) => Filter<InputL, PassR, InputL>
<InputL, PassL, FailL, PassR, FailR>(
left: Filter<InputL, PassL, FailL>,
right: Filter<PassL, PassR, FailR>
): Filter<InputL, PassR, InputL>Composes two filters sequentially, passing the successful output of the first filter to the second.
Details
If either filter fails, the returned filter fails with the original input instead of the intermediate failure value.
export const const composePassthrough: {
<InputL, PassL, PassR, FailR>(
right: Filter<PassL, PassR, FailR>
): <FailL>(
left: Filter<InputL, PassL, FailL>
) => Filter<InputL, PassR, InputL>
<InputL, PassL, FailL, PassR, FailR>(
left: Filter<InputL, PassL, FailL>,
right: Filter<PassL, PassR, FailR>
): Filter<InputL, PassR, InputL>
}
Composes two filters sequentially, passing the successful output of the first
filter to the second.
Details
If either filter fails, the returned filter fails with the original input
instead of the intermediate failure value.
composePassthrough: {
<function (type parameter) InputL in <InputL, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, InputL>InputL, function (type parameter) PassL in <InputL, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, InputL>PassL, function (type parameter) PassR in <InputL, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, InputL>PassR, function (type parameter) FailR in <InputL, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, InputL>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 <InputL, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, InputL>PassL, function (type parameter) PassR in <InputL, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, InputL>PassR, function (type parameter) FailR in <InputL, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, InputL>FailR>
): <function (type parameter) FailL in <FailL>(left: Filter<InputL, PassL, FailL>): Filter<InputL, PassR, InputL>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, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, InputL>InputL, function (type parameter) PassL in <InputL, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, InputL>PassL, function (type parameter) FailL in <FailL>(left: Filter<InputL, PassL, FailL>): Filter<InputL, PassR, InputL>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, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, InputL>InputL, function (type parameter) PassR in <InputL, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, InputL>PassR, function (type parameter) InputL in <InputL, PassL, PassR, FailR>(right: Filter<PassL, PassR, FailR>): <FailL>(left: Filter<InputL, PassL, FailL>) => Filter<InputL, PassR, InputL>InputL>
<function (type parameter) InputL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>InputL, function (type parameter) PassL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>PassL, function (type parameter) FailL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>FailL, function (type parameter) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>PassR, function (type parameter) FailR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>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, InputL>InputL, function (type parameter) PassL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>PassL, function (type parameter) FailL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>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, InputL>PassL, function (type parameter) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>PassR, function (type parameter) FailR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>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, InputL>InputL, function (type parameter) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>PassR, function (type parameter) InputL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>InputL>
} = dual<(...args: Array<any>) => any, <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>) => Filter<InputL, PassR, InputL>>(arity: 2, body: <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>) => Filter<InputL, PassR, InputL>): ((...args: Array<any>) => any) & (<InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>) => Filter<InputL, PassR, InputL>) (+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, InputL>InputL, function (type parameter) PassL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>PassL, function (type parameter) FailL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>FailL, function (type parameter) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>PassR, function (type parameter) FailR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>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, InputL>InputL, function (type parameter) PassL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>PassL, function (type parameter) FailL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>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, InputL>PassL, function (type parameter) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>PassR, function (type parameter) FailR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>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, InputL>InputL, function (type parameter) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>PassR, function (type parameter) InputL in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>InputL> =>
(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 import ResultResult.const fail: <E>(
left: E
) => Result<never, E>
Creates a Result holding a Failure value.
When to use
Use to represent a failed Result with a typed failure value.
Details
- The success type
A defaults to never
Example (Creating a failure)
import { Result } from "effect"
const result = Result.fail("Something went wrong")
console.log(Result.isFailure(result))
// Output: true
fail(input: InputLinput)
const const rightOut: Result.Result<
PassR,
FailR
>
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)
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 rightOut: Result.Result<
PassR,
FailR
>
import ResultResult.const fail: <E>(
left: E
) => Result<never, E>
Creates a Result holding a Failure value.
When to use
Use to represent a failed Result with a typed failure value.
Details
- The success type
A defaults to never
Example (Creating a failure)
import { Result } from "effect"
const result = Result.fail("Something went wrong")
console.log(Result.isFailure(result))
// Output: true
fail(input: InputLinput)
return const rightOut: Result.Success<
PassR,
FailR
>
const rightOut: {
_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;
}
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) PassR in <InputL, PassL, FailL, PassR, FailR>(left: Filter<InputL, PassL, FailL>, right: Filter<PassL, PassR, FailR>): Filter<InputL, PassR, InputL>PassR>
})