Module

pooka/result

src/pooka/result.pooka

Carry the answer and the explanation in different envelopes.

Transform successful values or errors without throwing away the other branch. flat_map chains a fallible callback, while conversion to Option deliberately discards error details.

import pooka/result

assert result.map(Ok(2), fn(x) { x + 1 }) == Ok(3)

API reference

functionmap
functionmap_error
functionflat_map
functionunwrap_or
functionunwrap_or_else
functionis_ok
functionis_error
functionto_option

function

map

src/pooka/result.pooka:25

map(value: Result(a, e), transform: fn(a) -> b) -> Result(b, e)

INFERREDfn(Result(a, b), fn(a) -> c) -> Result(c, b)

Transform the carried value; an absent or failed branch passes through unchanged.

import pooka/result

assert result.map(Ok(2), fn(x) { x + 1 }) == Ok(3)

function

map_error

src/pooka/result.pooka:39

map_error(value: Result(a, e), transform: fn(e) -> f) -> Result(a, f)

INFERREDfn(Result(a, b), fn(b) -> c) -> Result(a, c)

Transform only the error, preserving successful values.

import pooka/result

assert result.map_error(Error(2), fn(x) { x + 1 }) == Error(3)

function

flat_map

src/pooka/result.pooka:53

flat_map(value: Result(a, e), transform: fn(a) -> Result(b, e)) -> Result(b, e)

INFERREDfn(Result(a, b), fn(a) -> Result(c, b)) -> Result(c, b)

Chain a callback that already returns the same fallible wrapper.

import pooka/result

assert result.flat_map(Ok(2), fn(x) { Ok(x + 1) }) == Ok(3)

function

unwrap_or

src/pooka/result.pooka:67

unwrap_or(value: Result(a, e), default: a) -> a

INFERREDfn(Result(a, b), a) -> a

Return the carried value, or the already evaluated fallback.

import pooka/result

assert result.unwrap_or(Error("missing"), 7) == 7

function

unwrap_or_else

src/pooka/result.pooka:81

unwrap_or_else(value: Result(a, e), fallback: fn(e) -> a) -> a

INFERREDfn(Result(a, b), fn(b) -> a) -> a

Call the fallback with the error only when the Result failed.

import pooka/result

assert result.unwrap_or_else(Error(2), fn(error) { error + 1 }) == 3

function

is_ok

src/pooka/result.pooka:95

is_ok(value: Result(a, e)) -> Bool

INFERREDfn(Result(a, b)) -> Bool

Ask whether the Result carries success.

import pooka/result

assert result.is_ok(Ok(1))

function

is_error

src/pooka/result.pooka:109

is_error(value: Result(a, e)) -> Bool

INFERREDfn(Result(a, b)) -> Bool

Ask whether the Result carries an error.

import pooka/result

assert result.is_error(Error("missing"))

function

to_option

src/pooka/result.pooka:120

to_option(value: Result(a, e)) -> Option(a)

INFERREDfn(Result(a, b)) -> Option(a)

Keep a successful value and deliberately discard error details.

import pooka/result

assert result.to_option(Ok(1)) == Some(1)