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Arkham/phantom.elm

Created February 26, 2018 20:19
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Example of phantom type in Elm
Raw
phantom.elm
module Main exposing (main)
import Html exposing (Html, text)
type Distance a
= Distance Float
type Kilometer
= Kilometer
type Mile
= Mile
marathonDistance : Distance Kilometer
marathonDistance =
Distance 42.195
distanceKmToMiles : Distance Kilometer -> Distance Mile
distanceKmToMiles (Distance km) =
Distance (0.621371 * km)
marathonDistanceInMiles : Distance Mile
marathonDistanceInMiles =
distanceKmToMiles marathonDistance
main : Html msg
main =
text (distanceKmToMiles marathonDistanceInMiles)
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