{-# LANGUAGE CPP, MagicHash, Rank2Types #-}

-- |
-- Module      : Data.Double.Conversion.Text
-- Copyright   : (c) 2011 MailRank, Inc.
--
-- License     : BSD-style
-- Maintainer  : bos@serpentine.com
-- Stability   : experimental
-- Portability : GHC
--
-- Fast, efficient support for converting between double precision
-- floating point values and text.
--
-- These functions are about 30 times faster than the default 'show'
-- implementation for the 'Double' type.

module Data.Double.Conversion.Text
    (
      toExponential
    , toFixed
    , toPrecision
    , toShortest
    ) where

import Control.Monad (when)
#if MIN_VERSION_base(4,4,0)
import Control.Monad.ST.Unsafe (unsafeIOToST)
#else
import Control.Monad.ST (unsafeIOToST)
#endif
import Control.Monad.ST (runST)
import Data.Double.Conversion.FFI
import Data.Text.Internal (Text(Text))
import Foreign.C.Types (CDouble, CInt)
import GHC.Prim (MutableByteArray#)
import qualified Data.Text.Array as A

-- | Compute a representation in exponential format with the requested
-- number of digits after the decimal point. The last emitted digit is
-- rounded.  If -1 digits are requested, then the shortest exponential
-- representation is computed.
toExponential :: Int -> Double -> Text
toExponential :: Int -> Double -> Text
toExponential Int
ndigits = String
-> CInt
-> (forall s. CDouble -> MutableByteArray# s -> IO CInt)
-> Double
-> Text
convert String
"toExponential" CInt
len ((forall s. CDouble -> MutableByteArray# s -> IO CInt)
 -> Double -> Text)
-> (forall s. CDouble -> MutableByteArray# s -> IO CInt)
-> Double
-> Text
forall a b. (a -> b) -> a -> b
$ \CDouble
val MutableByteArray# s
mba ->
                        CDouble -> MutableByteArray# s -> CInt -> IO CInt
forall s. CDouble -> MutableByteArray# s -> CInt -> IO CInt
c_Text_ToExponential CDouble
val MutableByteArray# s
mba (Int -> CInt
forall a b. (Integral a, Num b) => a -> b
fromIntegral Int
ndigits)
  where len :: CInt
len = CInt
c_ToExponentialLength
        {-# NOINLINE len #-}

-- | Compute a decimal representation with a fixed number of digits
-- after the decimal point. The last emitted digit is rounded.
toFixed :: Int -> Double -> Text
toFixed :: Int -> Double -> Text
toFixed Int
ndigits = String
-> CInt
-> (forall s. CDouble -> MutableByteArray# s -> IO CInt)
-> Double
-> Text
convert String
"toFixed" CInt
len ((forall s. CDouble -> MutableByteArray# s -> IO CInt)
 -> Double -> Text)
-> (forall s. CDouble -> MutableByteArray# s -> IO CInt)
-> Double
-> Text
forall a b. (a -> b) -> a -> b
$ \CDouble
val MutableByteArray# s
mba ->
                  CDouble -> MutableByteArray# s -> CInt -> IO CInt
forall s. CDouble -> MutableByteArray# s -> CInt -> IO CInt
c_Text_ToFixed CDouble
val MutableByteArray# s
mba (Int -> CInt
forall a b. (Integral a, Num b) => a -> b
fromIntegral Int
ndigits)
  where len :: CInt
len = CInt
c_ToFixedLength
        {-# NOINLINE len #-}

-- | Compute the shortest string of digits that correctly represent
-- the input number.
toShortest :: Double -> Text
toShortest :: Double -> Text
toShortest = String
-> CInt
-> (forall s. CDouble -> MutableByteArray# s -> IO CInt)
-> Double
-> Text
convert String
"toShortest" CInt
len forall s. CDouble -> MutableByteArray# s -> IO CInt
c_Text_ToShortest
  where len :: CInt
len = CInt
c_ToShortestLength
        {-# NOINLINE len #-}

-- | Compute @precision@ leading digits of the given value either in
-- exponential or decimal format. The last computed digit is rounded.
toPrecision :: Int -> Double -> Text
toPrecision :: Int -> Double -> Text
toPrecision Int
ndigits = String
-> CInt
-> (forall s. CDouble -> MutableByteArray# s -> IO CInt)
-> Double
-> Text
convert String
"toPrecision" CInt
len ((forall s. CDouble -> MutableByteArray# s -> IO CInt)
 -> Double -> Text)
-> (forall s. CDouble -> MutableByteArray# s -> IO CInt)
-> Double
-> Text
forall a b. (a -> b) -> a -> b
$ \CDouble
val MutableByteArray# s
mba ->
                      CDouble -> MutableByteArray# s -> CInt -> IO CInt
forall s. CDouble -> MutableByteArray# s -> CInt -> IO CInt
c_Text_ToPrecision CDouble
val MutableByteArray# s
mba (Int -> CInt
forall a b. (Integral a, Num b) => a -> b
fromIntegral Int
ndigits)
  where len :: CInt
len = CInt
c_ToPrecisionLength
        {-# NOINLINE len #-}

convert :: String -> CInt
        -> (forall s. CDouble -> MutableByteArray# s -> IO CInt)
        -> Double -> Text
convert :: String
-> CInt
-> (forall s. CDouble -> MutableByteArray# s -> IO CInt)
-> Double
-> Text
convert String
func CInt
len forall s. CDouble -> MutableByteArray# s -> IO CInt
act Double
val = (forall s. ST s Text) -> Text
forall a. (forall s. ST s a) -> a
runST forall s. ST s Text
go
  where
    go :: ST s Text
go = do
      MArray s
buf <- Int -> ST s (MArray s)
forall s. Int -> ST s (MArray s)
A.new (CInt -> Int
forall a b. (Integral a, Num b) => a -> b
fromIntegral CInt
len)
      CInt
size <- IO CInt -> ST s CInt
forall a s. IO a -> ST s a
unsafeIOToST (IO CInt -> ST s CInt) -> IO CInt -> ST s CInt
forall a b. (a -> b) -> a -> b
$ CDouble -> MutableByteArray# s -> IO CInt
forall s. CDouble -> MutableByteArray# s -> IO CInt
act (Double -> CDouble
forall a b. (Real a, Fractional b) => a -> b
realToFrac Double
val) (MArray s -> MutableByteArray# s
forall s. MArray s -> MutableByteArray# s
A.maBA MArray s
buf)
      Bool -> ST s () -> ST s ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (CInt
size CInt -> CInt -> Bool
forall a. Eq a => a -> a -> Bool
== -CInt
1) (ST s () -> ST s ()) -> (String -> ST s ()) -> String -> ST s ()
forall b c a. (b -> c) -> (a -> b) -> a -> c
.
        String -> ST s ()
forall (m :: * -> *) a. MonadFail m => String -> m a
fail (String -> ST s ()) -> String -> ST s ()
forall a b. (a -> b) -> a -> b
$ String
"Data.Double.Conversion.Text." String -> String -> String
forall a. [a] -> [a] -> [a]
++ String
func String -> String -> String
forall a. [a] -> [a] -> [a]
++
               String
": conversion failed (invalid precision requested)"
      Array
frozen <- MArray s -> ST s Array
forall s. MArray s -> ST s Array
A.unsafeFreeze MArray s
buf
      Text -> ST s Text
forall (m :: * -> *) a. Monad m => a -> m a
return (Text -> ST s Text) -> Text -> ST s Text
forall a b. (a -> b) -> a -> b
$ Array -> Int -> Int -> Text
Text Array
frozen Int
0 (CInt -> Int
forall a b. (Integral a, Num b) => a -> b
fromIntegral CInt
size)