Std.Result

Computations that can succeed (Ok) or fail (Err) with a typed error.

Types

Result

type Result a b =
  | Ok a
  | Err b

A value that is either a success (Ok) or a failure (Err).

Functions

is_ok

fun is_ok : Result a b -> Bool

Returns True if the value is Ok.

is_err

fun is_err : Result a b -> Bool

Returns True if the value is Err.

map

fun map : (f: a -> c) -> (r: Result a b) -> Result c b

Applies a function to the Ok value, leaving Err unchanged.

map_err

fun map_err : (f: b -> c) -> (r: Result a b) -> Result a c

Applies a function to the Err value, leaving Ok unchanged.

unwrap

fun unwrap : (r: Result a b) -> a where {b: Debug}

Returns the Ok value. Panics on Err.

unwrap_or

fun unwrap_or : (default: a) -> (r: Result a b) -> a

Returns the Ok value or a default if Err.

and_then

fun and_then : (f: a -> Result c b) -> (r: Result a b) -> Result c b

Chains a function that returns Result. Short-circuits on Err.

or_else

fun or_else : (fallback: Result a b) -> (r: Result a b) -> Result a b

Returns the first Ok value, or tries the fallback on Err.

to_maybe

fun to_maybe : Result a b -> Maybe a

Converts a Result to a Maybe, discarding the error.

from_maybe

fun from_maybe : (err: e) -> (m: Maybe a) -> Result a e

Converts a Maybe to a Result, using the given error if Nothing.

flatten

fun flatten : Result (Result a b) b -> Result a b

Flattens a nested Result.