<A, E>(
success: Equivalence.Equivalence<A>,
failure: Equivalence.Equivalence<E>
): Equivalence.Equivalence<Result<A, E>>Creates an Equivalence for comparing two Result values.
Details
- Two
Successvalues are equal when thesuccessequivalence says so - Two
Failurevalues are equal when thefailureequivalence says so - A
Successand aFailureare never equal
Example (Comparing Results for equality)
import { Equivalence, Result } from "effect"
const eq = Result.makeEquivalence(
Equivalence.strictEqual<number>(),
Equivalence.strictEqual<string>()
)
console.log(eq(Result.succeed(1), Result.succeed(1)))
// Output: true
console.log(eq(Result.succeed(1), Result.fail("x")))
// Output: falseinstances
Source effect/Result.ts:7229 lines
export const const makeEquivalence: <A, E>(
success: Equivalence.Equivalence<A>,
failure: Equivalence.Equivalence<E>
) => Equivalence.Equivalence<Result<A, E>>
Creates an Equivalence for comparing two Result values.
Details
- Two
Success values are equal when the success equivalence says so
- Two
Failure values are equal when the failure equivalence says so
- A
Success and a Failure are never equal
Example (Comparing Results for equality)
import { Equivalence, Result } from "effect"
const eq = Result.makeEquivalence(
Equivalence.strictEqual<number>(),
Equivalence.strictEqual<string>()
)
console.log(eq(Result.succeed(1), Result.succeed(1)))
// Output: true
console.log(eq(Result.succeed(1), Result.fail("x")))
// Output: false
makeEquivalence = <function (type parameter) A in <A, E>(success: Equivalence.Equivalence<A>, failure: Equivalence.Equivalence<E>): Equivalence.Equivalence<Result<A, E>>A, function (type parameter) E in <A, E>(success: Equivalence.Equivalence<A>, failure: Equivalence.Equivalence<E>): Equivalence.Equivalence<Result<A, E>>E>(
success: Equivalence.Equivalence<A>success: import EquivalenceEquivalence.type Equivalence.Equivalence = /*unresolved*/ anyEquivalence<function (type parameter) A in <A, E>(success: Equivalence.Equivalence<A>, failure: Equivalence.Equivalence<E>): Equivalence.Equivalence<Result<A, E>>A>,
failure: Equivalence.Equivalence<E>failure: import EquivalenceEquivalence.type Equivalence.Equivalence = /*unresolved*/ anyEquivalence<function (type parameter) E in <A, E>(success: Equivalence.Equivalence<A>, failure: Equivalence.Equivalence<E>): Equivalence.Equivalence<Result<A, E>>E>
): import EquivalenceEquivalence.type Equivalence.Equivalence = /*unresolved*/ anyEquivalence<type Result<A, E = never> = Success<A, E> | 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) A in <A, E>(success: Equivalence.Equivalence<A>, failure: Equivalence.Equivalence<E>): Equivalence.Equivalence<Result<A, E>>A, function (type parameter) E in <A, E>(success: Equivalence.Equivalence<A>, failure: Equivalence.Equivalence<E>): Equivalence.Equivalence<Result<A, E>>E>> =>
import EquivalenceEquivalence.make((x: Result<A, E>x, y: Result<A, E>y) =>
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(x: Result<A, E>x) ?
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(y: Result<A, E>y) && failure: Equivalence.Equivalence<E>failure(x: Failure<A, E>(parameter) x: {
_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;
}
Failure<unknown, unknown>.failure: unknownfailure, y: Failure<A, E>(parameter) y: {
_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;
}
Failure<unknown, unknown>.failure: unknownfailure) :
const isSuccess: <A, E>(
self: Result<A, E>
) => self is Success<A, E>
Checks whether a Result is a Success.
When to use
Use to narrow a known Result to the Success variant.
Details
- Acts as a TypeScript type guard, narrowing to
Success<A, E>
- After narrowing, you can access
.success to read the value
Example (Narrowing to success)
import { Result } from "effect"
const result = Result.succeed(42)
if (Result.isSuccess(result)) {
console.log(result.success)
// Output: 42
}
isSuccess(y: Result<A, E>y) && success: Equivalence.Equivalence<A>success(x: Success<A, E>(parameter) x: {
_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;
}
y: Success<A, E>(parameter) y: {
_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<unknown, unknown>.success: unknownsuccess)
)Referenced by 1 symbols