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|
module Result
doc """
Result represents the result of something that may succeed or fail.
`Ok` means it was successful, `Error` means it failed.
"""
pub type Result(error, value) {
| Ok(value)
| Error(error)
;
import Result:*
pub fn is_ok(result) {
case result {
| Error(_) => False
| Ok(_) => True
}
}
test is_ok {
is_ok(Ok(1)) |> Assert.true
is_ok(Error(1)) |> Assert.false
}
pub fn is_error(result) {
case result {
| Ok(_) => False
| Error(_) => True
}
}
test is_error {
is_error(Ok(1)) |> Assert.false
is_error(Error(1)) |> Assert.true
}
pub fn map(result, fun) {
case result {
| Ok(x) => fun(x)
| Error(_) => result
}
}
test map {
Ok(1)
|> map(_, fn(x) { x + 1 })
|> Assert.equal(_, Ok(2))
Error(1)
|> map(_, fn(x) { x + 1 })
|> Assert.equal(Error(1))
}
pub fn map_error(result, fun) {
case result {
| Ok(_) => result
| Error(error) => Error(fun(error))
}
}
test map_error {
Ok(1)
|> map_error(_, fn(x) { x + 1 })
|> Assert.equal(_, Ok(1))
Error(1)
|> map_error(_, fn(x) { x + 1 })
|> Assert.equal(_, Error(2))
}
pub fn flatten(result) {
case result {
| Ok(x) => x
| Error(_) => result
}
}
test flatten {
flatten(Ok(Ok(1)))
|> Assert.equal(_, Ok(1))
flatten(Ok(Error(1)))
|> Assert.equal(_, Error(1))
flatten(Error(1))
|> Assert.equal(_, Error(1))
}
pub fn flat_map(result, fun) {
result
|> unwrap(_, fun)
|> flatten
}
test flat_map {
Error(1)
|> flat_map(_, fn(x) { Ok(x + 1) })
|> Assert.equal(_, Error(1))
Ok(1)
|> flat_map(_, fn(x) { Ok(x + 1) })
|> Assert.equal(_, Ok(2))
Ok(1)
|> flat_map(_, fn(_) { Error(1) })
|> Assert.equal(_, Error(1))
}
pub fn unwrap(result, default) {
case result {
| Ok(v) => v
| Error(_) => default
}
}
test unwrap {
unwrap(Ok(1), 50) |> Assert.equal(_, 1)
unwrap(Error("nope"), 50) |> Assert.equal(_, 50)
}
|
