variable and function context between prompts

1 files changed, 69 insertions, 0 deletions

diff --git a/src/Evaluation.hs b/src/Evaluation.hs
new file mode 100644
index 0000000..b0b5aab
--- /dev/null
+++ b/src/Evaluation.hs
@@ -0,0 +1,69 @@
+module Evaluation where
+
+import Expr
+import qualified Assignment as A
+
+eval :: A.Context -> Expr -> Maybe Atom
+eval c (Variable n) = do (A.Variable _ e) <- A.get c n
+                         eval c e
+eval c (Function n e) = do x <- eval c e
+                           (A.Function _ param fe) <- A.get c n
+                           let tmp = A.update c (A.Variable param (EAtom x))
+                           eval tmp fe
+eval c (EAtom a) = Just a
+eval c (Add e1 e2) = evalInfix c e1 e2 (+?)
+eval c (Sub e1 e2) = evalInfix c e1 e2 (-?)
+eval c (Mul e1 e2) = evalInfix c e1 e2 (*?)
+eval c (Div e1 e2) = evalInfix c e1 e2 (/?)
+eval c (Mod e1 e2) = evalInfix c e1 e2 (%?)
+eval c (Exp e1 e2) = evalInfix c e1 e2 (^?)
+eval c (Dot e1 e2) = evalInfix c e1 e2 (**?)
+-- eval _ _ = Nothing
+
+evalInfix :: A.Context -> Expr -> Expr -> (Atom -> Atom -> Maybe Atom) -> Maybe Atom
+evalInfix c e1 e2 f = do a <- eval c e1
+                         b <- eval c 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