I was envisioning that the maybe-returning version would be a separate method, equivalent to the current two-return-value variant, which of course already has t

I was envisioning that the maybe-returning version would be a separate method, equivalent to the current two-return-value variant, which of course already has that overhead. Having the default return a 'maybe' would be a possibility; I'm pretty sure the practical performance difference would be completely negligible, given all the other stuff a map lookup has to do, but it might have worse ergonomics. In that case you'd probably want a builtin optional-unwrapping operator like some languages have, so it's not too verbose if you expect the element to be there. > Is there any language where a map/set access returns an optional/maybe? Swift is one. It has ! as an unwrap operator, along with other syntax sugar for optionals, so it's not verbose: 5> let q = ["a": "b"] [snip] 6> q["a"] $R2: String? = "b" 7> q["x"] $R3: String? = nil 8> q["a"]! $R4: String = "b" 9> q["x"]! fatal error: unexpectedly found nil while unwrapping an Optional value