3.11 option

Usage:

include option

import option as ...

data Option<a>:

end

none :: Option<a>
some :: (value :: a) -> Option<a>
is-none :: (val :: Any) -> Boolean
is-some :: (val :: Any) -> Boolean

.and-then :: (f :: (a -> b)) -> Option<b>

For none, returns none. For some, applies f to the value field and returns a new some with the updated value.

Examples:

check:
  add1 = lam(n): n + 1 end
  n = none
  n.and-then(add1) is none

  s = some(5)
  s.and-then(add1) is some(6)
end

.or-else :: (v :: a) -> a

For none, returns v. For some, returns the value field. Useful for providing default values.

Examples:

check:
  n = none
  n.or-else(42) is 42

  s = some(5)
  s.or-else(10) is 5
end