I'm not sure such a feature would have any uses. Right now, all Elm functions have well-typed return values.
Ports are the one place where a type annotation is used to enforce a type at runtime. So I suppose ports are Elm's analog to "read". There has been lots of discussion about improving ports, to translate JavaScript objects into ADTs. It's possible that change might happen at some point. On Tue, Jan 17, 2017 at 9:07 AM, Josh Szmajda <[email protected]> wrote: > Ah yes this makes sense, we'd need the explicit type annotation. Has that > functionality been discussed? I know I saw a talk where Evan mentioned > adding features to the language over time intentionally to help drive > adoption. > > Thanks! > > On Monday, January 16, 2017 at 9:06:50 PM UTC-5, Nick H wrote: >> >> I doubt such a function will be introduced any time soon, because it's >> not a properly typed operation. In Haskell, you have to add the type >> annotation to the function call because read's return type is ambiguous. >> However, Elm doesn't have any similar ability. >> >> For converting Strings to numeric types, there are String.toInt and >> String.toFloat. >> >> For doing what your example does, I might consider using a dictionary >> mapping strings to states. Maybe Something like: >> >> viewStates = Dict.fromList [ ("ViewDocList", ViewDocList), >> ("ViewDocument", ViewDocument) ] >> >> locationUpdate location = >> case Dict.get location viewStates of >> Just state -> >> ViewState state >> >> Nothing -> >> App.NoOp >> >> You still need to manually associate strings with view states, but now >> locationUpdate has the form you want. >> >> On Mon, Jan 16, 2017 at 12:44 PM, Josh Szmajda <[email protected]> wrote: >> >>> Hey folks! >>> >>> This is in reference to https://github.com/elm-lang/core/issues/805 >>> >>> I'm looking for a function to convert a String to an internal symbol >>> (signature `String -> a`). Previously this was in `Text.fromString` but >>> apparently that has been removed. >>> >>> The use-case I have in mind is this router: >>> >>> ``` >>> locationUpdate : Navigation.Location -> App.Msg >>> locationUpdate location = >>> case (String.dropLeft 2 location.hash) of >>> >>> "ViewDocList" -> ViewState ViewDocList >>> >>> "ViewDocument" -> ViewState ViewDocument >>> >>> _ -> App.NoOp >>> >>> -- Would rather code this as: >>> -- case Text.fromString msg of >>> -- Just value -> ViewState value >>> -- Nothing -> App.NoOp >>> ``` >>> >>> In Haskell this would be `read`: >>> >>> ``` >>> Prelude> read "4.5" :: Float >>> 4.5 >>> Prelude> :t read "4.5" :: Float >>> read "4.5" :: Float :: Float >>> ``` >>> >>> Any ideas on when this might come back? >>> >>> Thanks! >>> -Josh >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Elm Discuss" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- > You received this message because you are subscribed to the Google Groups > "Elm Discuss" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Elm Discuss" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
