<A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (
self: Iterable<A>
) => Array<B>
<A, B, X>(
self: Iterable<A>,
f: (input: NoInfer<A>, i: number) => Result.Result<B, X>
): Array<B>Takes elements from the start while a Filter succeeds, collecting transformed values.
When to use
Use when you need to take a prefix from an iterable while a function can successfully extract or transform elements, stopping at the first element that produces a failure result.
Details
The filter receives (element, index) and processing stops at the first
filter failure.
export const const takeWhileFilter: {
<A, B, X>(
f: (
input: NoInfer<A>,
i: number
) => Result.Result<B, X>
): (self: Iterable<A>) => Array<B>
<A, B, X>(
self: Iterable<A>,
f: (
input: NoInfer<A>,
i: number
) => Result.Result<B, X>
): Array<B>
}
Takes elements from the start while a Filter succeeds, collecting transformed values.
When to use
Use when you need to take a prefix from an iterable while a function can
successfully extract or transform elements, stopping at the first element
that produces a failure result.
Details
The filter receives (element, index) and processing stops at the first
filter failure.
takeWhileFilter: {
<function (type parameter) A in <A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<B>A, function (type parameter) B in <A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<B>B, function (type parameter) X in <A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<B>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<B>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<B>B, function (type parameter) X in <A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<B>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<B>A>) => interface Array<T>Array<function (type parameter) B in <A, B, X>(f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): (self: Iterable<A>) => Array<B>B>
<function (type parameter) A in <A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>A, function (type parameter) B in <A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>B, function (type parameter) X in <A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>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: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>A>, 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>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>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: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>B, function (type parameter) X in <A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>X>): interface Array<T>Array<function (type parameter) B in <A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>B>
} = dual<(...args: Array<any>) => any, <A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>) => Array<B>>(arity: 2, body: <A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>) => Array<B>): ((...args: Array<any>) => any) & (<A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>) => Array<B>) (+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: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>A, function (type parameter) B in <A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>B, function (type parameter) X in <A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>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: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>A>, 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>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>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: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>B, function (type parameter) X in <A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>X>): interface Array<T>Array<function (type parameter) B in <A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>B> => {
let let i: numberi = 0
const const out: B[]out: interface Array<T>Array<function (type parameter) B in <A, B, X>(self: Iterable<A>, f: (input: NoInfer<A>, i: number) => Result.Result<B, X>): Array<B>B> = []
for (const const a: Aa of self: Iterable<A>self) {
const const result: Result.Result<B, X>result = f: (
input: NoInfer<A>,
i: number
) => Result.Result<B, X>
const a: Aa, let i: numberi)
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 result: Result.Result<B, X>result)) {
break
}
const out: B[]out.Array<B>.push(...items: B[]): numberAppends new elements to the end of an array, and returns the new length of the array.
push(const result: Result.Success<B, X>const result: {
_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<B, X>.success: Bsuccess)
let i: numberi++
}
return const out: B[]out
})