PartiallyTranscendental.hs

{-# LANGUAGE NoImplicitPrelude #-}
{- |
Define Transcendental functions on arbitrary fields.
These functions are defined for only a few (in most cases only one) arguments,
that's why discourage making these types instances of 'Algebra.Transcendental.C'.
But instances of 'Algebra.Transcendental.C' can be useful when working with power series.
If you intent to work with power series with 'Rational' coefficients,
you might consider using @MathObj.PowerSeries.T (Number.PartiallyTranscendental.T Rational)@
instead of @MathObj.PowerSeries.T Rational@.
-}
module Number.PartiallyTranscendental (T, fromValue, toValue) where

import qualified Algebra.Transcendental as Transcendental
import qualified Algebra.Algebraic      as Algebraic
import qualified Algebra.Field          as Field
import qualified Algebra.Ring           as Ring
import qualified Algebra.Additive       as Additive
-- import qualified Algebra.ZeroTestable   as ZeroTestable

import NumericPrelude
import PreludeBase

import qualified Prelude as P


newtype T a = Cons {toValue :: a}
   deriving (Eq, Ord, Show)

fromValue :: a -> T a
fromValue = lift0

lift0 :: a -> T a
lift0 = Cons

lift1 :: (a -> a) -> (T a -> T a)
lift1 f (Cons x0) = Cons (f x0)

lift2 :: (a -> a -> a) -> (T a -> T a -> T a)
lift2 f (Cons x0) (Cons x1) = Cons (f x0 x1)


instance (Additive.C a) => Additive.C (T a) where
    negate = lift1 negate
    (+)    = lift2 (+)
    (-)    = lift2 (-)
    zero   = lift0 zero

instance (Ring.C a) => Ring.C (T a) where
    one           = lift0 one
    fromInteger n = lift0 (fromInteger n)
    (*)           = lift2 (*)

instance (Field.C a) => Field.C (T a) where
    (/) = lift2 (/)

instance (Algebraic.C a) => Algebraic.C (T a) where
    sqrt x = lift1 sqrt x
    root n = lift1 (Algebraic.root n)
    (^/) x y = lift1 (^/y) x

instance (Algebraic.C a, Eq a) => Transcendental.C (T a) where
    pi = undefined
    exp = \0 -> 1
    sin = \0 -> 0
    cos = \0 -> 1
    tan = \0 -> 0
    x ** y = if x==1 || y==0
               then 1
               else error "partially transcendental power undefined"
    log  = \1 -> 0
    asin = \0 -> 0
    acos = \1 -> 0
    atan = \0 -> 0



legacyInstance :: a
legacyInstance = error "legacy Ring instance for simple input of numeric literals"


instance (P.Num a) => P.Num (T a) where
   fromInteger n = lift0 $ P.fromInteger n
   negate = P.negate -- for unary minus
   (+)    = legacyInstance
   (*)    = legacyInstance
   abs    = legacyInstance
   signum = legacyInstance

instance (P.Num a) => P.Fractional (T a) where
   fromRational = P.fromRational
   (/) = legacyInstance