Error

Symmetry of error throwing and handling.

Try-catch#

Symbol: |->
Translated to JavaScript try-catch.

First parameter is catch function.
Other parameters are try lines.
Unlike JavaScript try-catch operator |-> in Una always returns some value and it doesn't have finally block.

Example:

|->
  <-
    = getName null
    getName ()
  -> error
    console.log error
    'John'

If you need to run async code use <-- instead of <- in try or --> instead -> in catch:

|->
  <--
    getNameAsync ()
  --> error
    console.log error
    "John"

Throw error#

Symbol: <-|
Translated to JavaScript throw.

Example:

= addOneToNumber -> number
  ?! (isNaN number)
    <-| "number is not valid"
  + number 1