src/Cryptsy/API/Public/Types/Num.hs

   1 {-# LANGUAGE EmptyDataDecls, GeneralizedNewtypeDeriving #-}
   2 -- |Default numeric type for prices, quanities, and total returned from the
   3 -- API.
   4 module Cryptsy.API.Public.Types.Num where
   5
   6 -- aeson
   7 import Data.Aeson (FromJSON(..))
   8
   9 -- base
  10 import Data.Fixed (HasResolution(..), Fixed)
  11 import Numeric (readFloat)
  12
  13 -- this package
  14 import Cryptsy.API.Public.Types.Internal
  15
  16 -- |Custom resolution for 'Fixed'; 1e8.
  17 data E8
  18
  19 instance HasResolution E8 where
  20         resolution = const 100000000
  21
  22 -- |Native number type for the API, newtype for custom FromJSON instance, which
  23 -- only accepts JSON strings.
  24 newtype CryptsyNum = CryptsyNum { toFixed :: Fixed E8 } deriving
  25         (Eq, Ord, Show, Read, Num, Real, Fractional, Enum, RealFrac)
  26
  27 instance FromJSON CryptsyNum where
  28         parseJSON = readsToParser "CrypstyNum" readFloat
  29