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 <jos...@gmail.com> 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
>
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