1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
|
module Numeric.Log where
import Compiler.Floating
data Log a = Exp a
instance RealFloat a => Num (Log a) where
Exp x + Exp y = Exp (x + log1p(exp(y-x)))
Exp x - Exp y = Exp (x - log1p(exp(y-x)))
Exp x * Exp y = Exp (x + y)
negate = error "Negation not allowed"
abs = id
signum _ = Exp 0
fromInteger x = Exp (log (fromInteger x))
instance RealFloat a => Fractional (Log a) where
Exp x / Exp y = Exp (x - y)
recip (Exp x) = Exp $ -x
instance Pow (Log Double) where
pow (Exp x) t = Exp $ x*t
ln (Exp x) = x
expTo x = Exp x
|
