Units.hs

{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# OPTIONS -Wall #-}

--------------------------------------------------------------------------------
-- |
-- Module      :  Wumpus.Basic.Kernel.Base.Units
-- Copyright   :  (c) Stephen Tetley 2011
-- License     :  BSD3
--
-- Maintainer  :  Stephen Tetley <stephen.tetley@gmail.com>
-- Stability   :  highly unstable
-- Portability :  GHC
--
-- Units @cm@, @pica@ and \"contextual\" units - @em@, @en@.
-- 
--------------------------------------------------------------------------------

module Wumpus.Basic.Kernel.Base.Units
  (


  -- * Centimeter
    Centimeter
  , cm
  , dcm

  -- * Pica
  , Pica
  , pica
  , dpica

  -- * Em
  , Em

  -- * En
  , En

  ) where


import Wumpus.Basic.Kernel.Base.BaseDefs

import Wumpus.Core                              -- package: wumpus-core


--------------------------------------------------------------------------------

-- | Wrapped Double representing Centimeter.
-- 
newtype Centimeter = Centimeter { getCentimeter :: Double } 
  deriving (Eq,Ord,Num,Floating,Fractional,Real,RealFrac,RealFloat)


instance Show Centimeter where
  showsPrec p d = showsPrec p (getCentimeter d)

-- | Cast a value in Centimeters to some Fractional type.
-- 
-- Note - this casting should only be used for non-contextual
-- units such as Double.
--
cm :: Fractional u => Centimeter -> u 
cm = realToFrac . (28.45275619 *) . getCentimeter

-- | Convert Double to Centimer.
-- 
dcm :: Double -> Centimeter
dcm = Centimeter . (0.03514598 *)

instance ScalarUnit Centimeter where
  fromPsPoint = dcm
  toPsPoint   = cm 

instance InterpretUnit Centimeter where
  normalize _ = cm 
  dinterp   _ = dcm

instance Tolerance Centimeter where 
  eq_tolerance     = 0.001
  length_tolerance = 0.01



-- | Wrapped Double /Pica/ unit type.
-- 
-- Pica is 12 Points.
--
newtype Pica = Pica { getPica :: Double } 
  deriving (Eq,Ord,Num,Floating,Fractional,Real,RealFrac,RealFloat)


instance Show Pica where
  showsPrec p d = showsPrec p (getPica d)

                            
-- | Cast a value in Pica to some Fractional type.
-- 
-- Note - this casting should only be used for non-contextual
-- units such as Double.
--
pica :: Fractional u => Pica -> u 
pica = realToFrac . (* 12.0) . getPica

-- | Convert a Double to a Pica.
--
dpica :: Double -> Pica
dpica = Pica . (\x -> x / 12.0)



instance ScalarUnit Pica where
  fromPsPoint = dpica
  toPsPoint   = pica

instance InterpretUnit Pica where
  normalize _ = pica
  dinterp   _ = dpica


instance Tolerance Pica where 
  eq_tolerance     = 0.001
  length_tolerance = 0.01



--------------------------------------------------------------------------------
-- Contextual units

-- | Wrapped Double representing an Em. 
-- 
newtype Em = Em { getEm :: Double } 
  deriving (Eq,Ord,Num,Floating,Fractional,Real,RealFrac,RealFloat)

instance Show Em where
  showsPrec p d = showsPrec p (getEm d)



instance InterpretUnit Em where
  normalize sz a = fromIntegral sz * realToFrac a
  dinterp sz d   = realToFrac d / fromIntegral sz


instance Tolerance Em where 
  eq_tolerance     = 0.001
  length_tolerance = 0.01


-- | Wrapped Double representing an En.
-- 
newtype En = En { getEn :: Double } 
  deriving (Eq,Ord,Num,Floating,Fractional,Real,RealFrac,RealFloat)

instance Show En where
  showsPrec p d = showsPrec p (getEn d)


instance InterpretUnit En where
  normalize sz a = (realToFrac  a) * 0.5 * fromIntegral sz
  dinterp sz d   = 2 * (realToFrac d) / (fromIntegral sz)


instance Tolerance En where
  eq_tolerance     = 0.001 
  length_tolerance = 0.01