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]
> <javascript:>> 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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>
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