1 files changed, 7 insertions, 3 deletions

diff --git a/spec/src/Thermoprint/Identifiers.hs b/spec/src/Thermoprint/Identifiers.hs
index 9608922..a2609a4 100644
--- a/spec/src/Thermoprint/Identifiers.hs
+++ b/spec/src/Thermoprint/Identifiers.hs
@@ -5,16 +5,20 @@ module Thermoprint.Identifiers
        ( PrinterId(..)
        , JobId(..)
        , DraftId(..)
+       , castId
        ) where
 
 import Servant.API (ToText, FromText)
 import Data.Aeson (FromJSON, ToJSON)
 
 newtype PrinterId = PrinterId Integer
-                  deriving (Show, Eq, Ord, Enum, FromText, ToText, FromJSON, ToJSON)
+                  deriving (Show, Eq, Ord, Num, Real, Integral, Enum, FromText, ToText, FromJSON, ToJSON)
 
 newtype JobId = JobId Integer
-              deriving (Show, Eq, Ord, Enum, FromText, ToText, FromJSON, ToJSON)
+              deriving (Show, Eq, Ord, Num, Real, Integral, Enum, FromText, ToText, FromJSON, ToJSON)
 
 newtype DraftId = DraftId Integer
-              deriving (Show, Eq, Ord, Enum, FromText, ToText, FromJSON, ToJSON)
+              deriving (Show, Eq, Ord, Num, Real, Integral, Enum, FromText, ToText, FromJSON, ToJSON)
+
+castId :: (Integral a, Enum b) => a -> b
+castId = toEnum . fromInteger . toInteger