1 files changed, 87 insertions, 0 deletions
diff --git a/src/Polynomial.hs b/src/Polynomial.hs
new file mode 100644
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--- /dev/null
+++ b/src/Polynomial.hs
@@ -0,0 +1,87 @@
+module Polynomial where
+
+-- import Data.List
+--
+--
+-- data Equation = Equation { left :: Polynomial, right :: Polynomial }
+-- type Polynomial = [Term]
+-- data Term = Term { coefficient :: Float, exponent :: Int }
+--
+-- instance Eq Term where
+--     (Term _ e1) == (Term _ e2) = e1 == e2
+--
+-- instance Ord Term where
+--     compare (Term _ e1) (Term _ e2) = compare e1 e2
+--
+-- instance Show Term where
+--     show (Term 0 e) = ""
+--     show (Term c 0) = show (round c)
+--     show (Term c e) = show (round c) ++ " * X^" ++ show e
+--
+-- instance Show Equation where
+--     show (Equation l r) = showPolynomial (filterNull l)
+--                           ++ " = "
+--                           ++ showPolynomial (filterNull r)
+--         where showPolynomial [] = "0"
+--               showPolynomial p  = dropWhile (`elem` " +") $ foldl f "" (map show p)
+--                 where f s "" = s
+--                       f s (c:cs)
+--                         | c == '-'  = s ++ " - " ++ cs
+--                         | otherwise = s ++ " + " ++ (c:cs)
+--
+--
+-- filterNull :: Polynomial -> Polynomial
+-- filterNull = filter (\t -> coefficient t /= 0)
+--
+-- equationMap :: (Polynomial -> Polynomial) -> Equation -> Equation
+-- equationMap f (Equation l r) = Equation (f l) (f r)
+--
+-- degree :: Polynomial -> Int
+-- degree [] = 0
+-- degree p  = Equation.exponent (maximum p)
+--
+-- reduce :: Equation -> Equation
+-- reduce equ = Equation (merge (left stdForm) (right stdForm)) []
+--     where stdForm = equationMap (\a -> (reducePolynomial $ sort a)) equ
+--           merge [] rs = rs
+--           merge ls [] = ls
+--           merge (l:ls) (r:rs)
+--             | l == r = (subTerm l r) : merge ls rs
+--             | l < r  = l : merge ls (r:rs)
+--             | r < l  = r : merge (l:ls) rs
+--             where subTerm (Term c1 e) (Term c2 _) = Term (c1 - c2) e
+--           reducePolynomial []         = []
+--           reducePolynomial [t]        = [t]
+--           reducePolynomial (t1:t2:ts)
+--             | t1 == t2  = (addTerm t1 t2) : reducePolynomial ts
+--             | otherwise = t1 : reducePolynomial (t2:ts)
+--             where addTerm (Term c1 e) (Term c2 _) = Term (c1 + c2) e
+--
+-- solveDegree2 :: Float -> Float -> Float -> [Float]
+-- solveDegree2 a b c
+--     | phi < 0   = []
+--     | phi == 0  = [(-b) / (2.0 * a)]
+--     | phi > 0   = [ (-b + mySqrt phi) / (2.0 * a) -- not alowed
+--                   , (-b - mySqrt phi) / (2.0 * a)
+--                   ]
+--     where phi = b * b - 4.0 * a * c
+--
+-- solveDegree1 :: Float -> Float -> Float
+-- solveDegree1 b c = -c / b
+--
+-- solve :: Polynomial -> [Float]
+-- solve [t0]         = []
+-- solve [t0, t1]     = [solveDegree1 (coefficient t1) (coefficient t0)]
+-- solve [t0, t1, t2] = solveDegree2 (coefficient t2) (coefficient t1) (coefficient t0)
+-- solve _            = undefined
+--
+-- mySqrt :: Float -> Float
+-- mySqrt n
+--   | n < 0     = undefined
+--   | otherwise = mySqrt' (n / 2)
+--     where mySqrt' x = if abs (x * x - n) < 0.01
+--                          then x
+--                          else mySqrt' xn
+--             where xn = b - (a * a) / (2 * b)
+--                     where a = (n - x * x) / (2 * x)
+--                           b = x + a