lookup package:relude

lookup :: StaticMap t => Key t -> t -> Maybe (Val t)
relude Relude.Extra.Map
lookupDefault :: StaticMap t => Val t -> Key t -> t -> Val t
relude Relude.Extra.Map
Return the value to which the specified key is mapped, or the default value if this map contains no mapping for the key. 
>>> let myHashMap = HashMap.fromList [('a', "xxx"), ('b', "yyy")]

>>> lookupDefault "zzz" 'b' myHashMap
"yyy"

>>> lookupDefault "zzz" 'c' myHashMap
"zzz"
lookupEnv :: MonadIO m => String -> m (Maybe String)
relude Relude.Lifted.Env
Lifted version of lookupEnv.