From 3ef6ec4bd3314efcac2504bd3a25e380d5e9514f Mon Sep 17 00:00:00 2001
From: Akshay <nerdy@peppe.rs>
Date: Fri, 9 Oct 2020 12:28:15 +0530
Subject: add experimental floating point handling

---
 src/Operators.hs | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

(limited to 'src/Operators.hs')

diff --git a/src/Operators.hs b/src/Operators.hs
index 3b96281..9eaec38 100644
--- a/src/Operators.hs
+++ b/src/Operators.hs
@@ -12,17 +12,36 @@ primitives =
     ("+", arithmetic (+))
     , ("-", arithmetic (-))
     , ("*", arithmetic (*))
-    , ("/", arithmetic div)
+    , ("/", arithmetic (/))
     ]
 
-arithmetic :: (Integer -> Integer -> Integer) -> [Expr] -> LispResult Expr
+data LispNumber = I Integer
+                | F Double
+
+instance Num LispNumber where
+    (I a) + (I b) = I $ a + b
+    (F a) + (F b) = F $ a + b
+    (I a) - (I b) = I $ a - b
+    (F a) - (F b) = F $ a - b
+    (I a) * (I b) = I $ a * b
+    (F a) * (F b) = F $ a * b
+
+instance Fractional LispNumber where
+    (I a) / (I b) = I $ a `div` b
+    (F a) / (F b) = F $ a / b
+
+arithmetic :: (LispNumber -> LispNumber -> LispNumber) -> [Expr] -> LispResult Expr
 arithmetic op args
     | length args < 2 = throwError $ ArgCount 2 args
     | otherwise = do
         as <- mapM unwrapNum args
-        return . IntLiteral $ foldl1 op as
+        return . wrapNum $ foldl1 op as
 
-unwrapNum :: Expr -> LispResult Integer
-unwrapNum (IntLiteral n) = return n
-unwrapNum x              = throwError $ TypeMismatch "number" x
+unwrapNum :: Expr -> LispResult LispNumber
+unwrapNum (IntLiteral n)   =  return $ I n
+unwrapNum (FloatLiteral n) =  return $ F n
+unwrapNum x                = throwError $ TypeMismatch "number" x
 
+wrapNum :: LispNumber -> Expr
+wrapNum (I n) = IntLiteral n
+wrapNum (F n) = FloatLiteral n
-- 
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