```-----------------------------------------------------------------------------
-- |
-- Module      :  Data.Packed.Vector
-- Copyright   :  (c) Alberto Ruiz 2007
-- License     :  GPL-style
--
-- Maintainer  :  Alberto Ruiz <aruiz@um.es>
-- Stability   :  provisional
-- Portability :  portable
--
-- 1D arrays suitable for numeric computations using external libraries.
--
-----------------------------------------------------------------------------

module Data.Packed.Vector (
Vector,
fromList, (|>), toList, buildVector,
dim, (@>),
subVector, join,
constant, linspace,
vecdisp,
vectorMax, vectorMin, vectorMaxIndex, vectorMinIndex,
mapVector, zipVector,
fscanfVector, fprintfVector, freadVector, fwriteVector,
foldLoop, foldVector, foldVectorG
) where

import Data.Packed.Internal
import Numeric.GSL.Vector
-- import Data.Packed.ST

{- | Creates a real vector containing a range of values:

@\> linspace 5 (-3,7)
5 |> [-3.0,-0.5,2.0,4.5,7.0]@

Logarithmic spacing can be defined as follows:

@logspace n (a,b) = 10 ** linspace n (a,b)@
-}
linspace :: Int -> (Double, Double) -> Vector Double
linspace n (a,b) = add a \$ scale s  \$ fromList [0 .. fromIntegral n-1]
where scale = vectorMapValR Scale
s = (b-a)/fromIntegral (n-1)

vectorMax :: Vector Double -> Double
vectorMax = toScalarR Max

vectorMin :: Vector Double -> Double
vectorMin = toScalarR Min

vectorMaxIndex :: Vector Double -> Int
vectorMaxIndex = round . toScalarR MaxIdx

vectorMinIndex :: Vector Double -> Int
vectorMinIndex = round . toScalarR MinIdx

{- | creates a vector with a given number of equal components:

@> constant 2 7
7 |> [2.0,2.0,2.0,2.0,2.0,2.0,2.0]@
-}
constant :: Element a => a -> Int -> Vector a
-- constant x n = runSTVector (newVector x n)
constant = constantD -- about 2x faster

{- | creates a Vector of the specified length using the supplied function to
to map the index to the value at that index.

@> buildVector 4 fromIntegral
4 |> [0.0,1.0,2.0,3.0]@

-}
buildVector :: Element a => Int -> (Int -> a) -> Vector a
buildVector len f =
fromList \$ map f [0 .. (len - 1)]

{- | Show a vector using a function for showing matrices.

@disp = putStr . vecdisp ('dispf' 2)

\> disp ('linspace' 10 (0,1))
10 |> 0.00  0.11  0.22  0.33  0.44  0.56  0.67  0.78  0.89  1.00
@
-}
vecdisp :: (Element t) => (Matrix t -> String) -> Vector t -> String
vecdisp f v
= ((show (dim v) ++ " |> ") ++) . (++"\n")
. unwords . lines .  tail . dropWhile (not . (`elem` " \n"))
. f . trans . reshape 1
\$ v
```