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|
module LngLat exposing (LngLat, encodeAsPair, encodeAsObject, decodeFromPair, decodeFromObject, map)
{-| @docs LngLat, encodeAsPair, encodeAsObject, decodeFromPair, decodeFromObject, map
-}
import Json.Encode as Encode exposing (Value)
import Json.Decode as Decode exposing (Decoder)
{-| A LngLat represents a geographic position.
-}
type alias LngLat =
{ lng : Float
, lat : Float
}
{-| Most implementations seem to encode these as a 2 member array.
-}
encodeAsPair : LngLat -> Value
encodeAsPair { lng, lat } =
Encode.list [ Encode.float lng, Encode.float lat ]
{-| Most implementations seem to encode these as a 2 member array.
-}
decodeFromPair : Decoder LngLat
decodeFromPair =
Decode.list Decode.float
|> Decode.andThen
(\l ->
case l of
[ lng, lat ] ->
Decode.succeed (LngLat lng lat)
_ ->
Decode.fail "Doesn't apear to be a valid lng lat pair"
)
{-| We can also encode as an `{lng: 32, lat: 435}` object.
-}
encodeAsObject : LngLat -> Value
encodeAsObject { lng, lat } =
Encode.object [ ( "lng", Encode.float lng ), ( "lat", Encode.float lat ) ]
{-| We can also encode from an `{lng: 32, lat: 435}` object.
-}
decodeFromObject : Decoder LngLat
decodeFromObject =
Decode.map2 LngLat (Decode.field "lng" Decode.float) (Decode.field "lat" Decode.float)
{-| -}
map : (Float -> Float) -> LngLat -> LngLat
map f { lng, lat } =
{ lng = f lng, lat = f lat }
|
