1 files changed, 98 insertions, 0 deletions
diff --git a/src/Expr.hs b/src/Expr.hs
new file mode 100644
index 0000000..e3d8aef
--- /dev/null
+++ b/src/Expr.hs
@@ -0,0 +1,98 @@
+module Expr where
+
+import Data.List
+
+
+data Atom
+    = Rational Float
+    | Imaginary Float
+    | Matrix [[Expr]]
+
+data Expr
+    = EAtom Atom
+    | Add Expr Expr
+    | Sub Expr Expr
+    | Mul Expr Expr
+    | Div Expr Expr
+    | Mod Expr Expr
+    | Exp Expr Expr
+    | Dot Expr Expr
+    | Variable String
+    | Function String Expr
+
+eval :: Expr -> Maybe Atom
+eval (EAtom a) = Just a
+eval (Add e1 e2) = evalInfix e1 e2 (+?)
+eval (Sub e1 e2) = evalInfix e1 e2 (-?)
+eval (Mul e1 e2) = evalInfix e1 e2 (*?)
+eval (Div e1 e2) = evalInfix e1 e2 (/?)
+eval (Mod e1 e2) = evalInfix e1 e2 (%?)
+eval (Exp e1 e2) = evalInfix e1 e2 (^?)
+eval (Dot e1 e2) = evalInfix e1 e2 (**?)
+eval _ = Nothing
+
+evalInfix :: Expr -> Expr -> (Atom -> Atom -> Maybe Atom) -> Maybe Atom
+evalInfix e1 e2 f = do a <- eval e1
+                       b <- eval e2
+                       f a b
+
+infixl 6 +?
+(+?) :: Atom -> Atom -> Maybe Atom
+(Rational a) +? (Rational b) = Just $ Rational (a + b)
+(Imaginary a) +? (Imaginary b) = Just $ Imaginary (a + b)
+_ +? _ = Nothing
+
+infixl 6 -?
+(-?) :: Atom -> Atom -> Maybe Atom
+(Rational a) -? (Rational b) = Just $ Rational (a - b)
+(Imaginary a) -? (Imaginary b) = Just $ Imaginary (a - b)
+_ -? _ = Nothing
+
+infixl 7 *?
+(*?) :: Atom -> Atom -> Maybe Atom
+(Rational a) *? (Rational b) = Just $ Rational (a * b)
+(Rational a) *? (Imaginary b) = Just $ Imaginary (a * b)
+(Imaginary a) *? (Imaginary b) = (Imaginary (a * b)) ^? Rational 2
+_ *? _ = Nothing
+
+infixl 7 /?
+(/?) :: Atom -> Atom -> Maybe Atom
+_ /? (Rational 0) = Nothing
+(Rational a) /? (Rational b) = Just $ Rational (a / b)
+_ /? _ = Nothing
+
+infixl 7 %?
+(%?) :: Atom -> Atom -> Maybe Atom
+_ %? _ = Nothing
+
+infixr 8 ^?
+(^?) :: Atom -> Atom -> Maybe Atom
+(Rational a) ^? (Rational b) = Just $ Rational (a ** b)
+(Imaginary a) ^? (Rational 0) = Just $ Rational a
+(Imaginary a) ^? (Rational 1) = Just $ Imaginary a
+(Imaginary a) ^? (Rational 2) = Just $ Rational (-a)
+(Imaginary a) ^? (Rational 3) = Just $ Imaginary (-a)
+(Imaginary a) ^? (Rational b) = Imaginary a ^? (Rational (b - 4))
+_ ^? _ = Nothing
+
+infixr 8 **?
+(**?) :: Atom -> Atom -> Maybe Atom
+_ **? _ = Nothing
+
+instance Show Expr where
+    show (EAtom a) = show a
+    show (Add e1 e2) = show e1 ++ " + " ++ show e2
+    show (Sub e1 e2) = show e1 ++ " - " ++ show e2
+    show (Mul e1 e2) = show e1 ++ " * " ++ show e2
+    show (Div e1 e2) = show e1 ++ " / " ++ show e2
+    show (Mod e1 e2) = show e1 ++ " % " ++ show e2
+    show (Exp e1 e2) = show e1 ++ " ^ " ++ show e2
+    show (Dot e1 e2) = show e1 ++ " ** " ++ show e2
+    show (Variable name) = name
+    show (Function name e) = name ++ "(" ++ show e ++ ")"
+
+instance Show Atom where
+    show (Rational r) = show r
+    show (Imaginary i) = show i ++ "i"
+    show (Matrix m) = intercalate "\n" (map showRow m)
+        where showRow r = "[ " ++ intercalate ", " (map show r) ++ " ]"