erf (empty) → 1.0.0.0

raw patch · 3 files changed

+51/−0 lines, 3 filesdep +basesetup-changed

Dependencies added: base

Files

• Setup.hs +3/−0
• erf.cabal +14/−0
• src/Data/Number/Erf.hs +34/−0

@@ -0,0 +1,3 @@+module Main where+import Distribution.Simple+main = defaultMain

@@ -0,0 +1,14 @@+Name:		erf+Version:	1.0.0.0+License:	BSD3+Author:		Lennart Augustsson+Maintainer:	Lennart Augustsson+Category:	Math+Synopsis:	The error function, erf, and friends+Stability:      experimental+Build-type:	Simple+Description:	A type class for the error function, erf, and related functions.+		Instances for Float and Double.+Hs-Source-Dirs: src+Build-Depends:		base+Exposed-modules:	Data.Number.Erf

@@ -0,0 +1,34 @@+{-# LANGUAGE ForeignFunctionInterface #-}+module Data.Number.Erf(Erf(..)) where+import Foreign.C++foreign import ccall "erf" c_erf :: CDouble -> CDouble+foreign import ccall "erfc" c_erfc :: CDouble -> CDouble+foreign import ccall "erff" c_erff :: CFloat -> CFloat+foreign import ccall "erfcf" c_erfcf :: CFloat -> CFloat++-- |Error function related functions.+--+-- The derivative of 'erf' is @\ x -> 2 / sqrt pi * exp (x^2)@,+-- and this uniquely determines 'erf' by @erf 0 = 0@.+--+-- Minimal complete definition is 'erfc' or 'normcdf'.+class (Floating a) => Erf a where+    erf :: a -> a+    erfc :: a -> a       -- ^@erfc x = 1 - erf x@+    erfcx :: a -> a      -- ^@erfcx x = exp (x*x) * erfc x@+    normcdf :: a -> a    -- ^@normcdf x = erfc(-x / sqrt 2) / 2@++    -- All the functions are inter-related, here's some defaults.+    erf x = 1 - erfc x+    erfc x = 2 * normcdf (-x * sqrt 2)+    erfcx x = exp (x*x) * erfc x+    normcdf x = erfc(-x / sqrt 2) / 2++instance Erf Double where+    erf = realToFrac . c_erf . realToFrac+    erfc = realToFrac . c_erfc . realToFrac++instance Erf Float where+    erf = realToFrac . c_erff . realToFrac+    erfc = realToFrac . c_erfcf . realToFrac