Result type that can hold either a value or an error, but not both
Add the following to your
or just drop the file in your project!
import result # It's convenient to create an alias - most likely, you'll do just fine # with strings as error! type R = Result[int, string] # Once you have a type, use `ok` and `err`: proc works(): R = # ok says it went... ok! R.ok 42 proc fails(): R = # or type it like this, to not repeat the type! result.err "bad luck" if (let w = works(); w.ok): echo w, " or use value: ", w.value # In case you think your callers want to differentiate between errors: type Error = enum a, b, c type RE[T] = Result[T, Error] # In the expriments corner, you'll find the following syntax for passing # errors up the stack: proc f(): R = let x = ?works() - ?fails() assert false, "will never reach"
See result.nim for more in-depth documentation - specially towards the end where there are plenty of examples!
MIT license, just like Nim