all: add stub for if

src/BC/Eval.hs

@@ -2,10 +2,22 @@ module BC.Eval (eval) where
 
 import BC.Types
 
+truthy :: Value -> Bool
+truthy (BNum num) = num /= 0
+truthy (BBool x) = x
+truthy _ = False
+
+
 eval :: [Value] -> Value
 eval [x@(BNum _)] = x
 eval [x@(BBool _)] = x
 eval [x@(BErr _)] = x
+eval [x@(BIf cond body alt)] =
+  if truthy (eval cond)
+    then eval body
+    else case alt of
+          Just vals -> eval vals
+          Nothing -> BBool False
 eval [(BOp x)] = BErr ("operation " ++ x ++ " requires arguments")
 eval [] = BOp ""
 eval l = treeEval l [] []
@@ -13,6 +25,7 @@ eval l = treeEval l [] []
 treeEval :: [Value] -> [Value] -> [Value] -> Value
 treeEval [] [] (num:_) = num
 treeEval [] ops nums = handleOp [] ops nums
+treeEval (x@(BIf _ _ _):xy) ops nums = treeEval (eval [x]:xy) ops nums
 treeEval (x@(BNum _):xy) ops nums = treeEval xy ops (x:nums)
 treeEval ((BBool x):xy) ops nums =
     treeEval xy ops ((BNum $ BInt $ if x then 1 else 0):nums)
@@ -50,6 +63,6 @@ binOp :: Value -> Maybe (Number -> Number -> Number)
 binOp (BOp "*") = Just (*)
 binOp (BOp "/") = Just (/)
 binOp (BOp "+") = Just (+)
-binOp (BOp "-") = Just (-)
+binOp (BOp "-") = Just ( - )
 binOp (BOp "^") = Just (**)
 binOp _ = Nothing

src/BC/Parse.hs

@@ -50,12 +50,43 @@ operator = do
     return $ BOp res
 
 
-types :: P.Parser Value
+-- I obviously can't parsec
-types = P.try bool P.<|> P.try operator P.<|> number
+parseIf :: P.Parser Value
+parseIf = do
+      _ <- P.string "if"
+      _ <- P.optionMaybe P.spaces
+      _ <- P.string "("
+      _ <- P.optionMaybe P.spaces
+      cond <- P.sepBy expr P.spaces
+      _ <- P.optionMaybe P.spaces
+      _ <- P.string ")"
+      _ <- P.optionMaybe P.spaces
+      _ <- P.string "{"
+      _ <- P.optionMaybe P.spaces
+      body <- P.sepBy expr P.spaces
+      _ <- P.optionMaybe P.spaces
+      _ <- P.string "}"
+      _ <- P.optionMaybe P.spaces
+      alt <- P.optionMaybe (P.string "else")
+      case alt of
+        Just _ -> do
+          _ <- P.optionMaybe P.spaces
+          _ <- P.string "{"
+          _ <- P.optionMaybe P.spaces
+          altbody <- P.sepBy expr P.spaces
+          _ <- P.optionMaybe P.spaces
+          _ <- P.string "}"
+          return $ BIf cond body (Just altbody)
+        Nothing -> return $ BIf cond body Nothing
+
+
+
+expr :: P.Parser Value
+expr = P.try bool P.<|> P.try parseIf P.<|> P.try number P.<|> operator
 
 
 parser :: P.Parser [Value]
-parser = (P.sepBy types P.spaces) <* P.eof
+parser = (P.sepBy expr P.spaces) <* P.eof
 
 parse :: String -> [Value]
 parse input = case P.parse parser (trim input) (trim input) of

src/BC/Types.hs

@@ -1,11 +1,21 @@
 module BC.Types where
 
+import Data.List (intercalate)
+
 data Value = BNum Number
            | BBool Bool
            | BOp String
+           | BIf [Value] [Value] (Maybe [Value])
            | BErr String
 instance Show Value where
   show (BBool b) = if b then "true" else "false"
+  show (BIf x y z) =
+    "if (" ++ unwords (map show x) ++ ") {\n\t" ++
+    intercalate "\n\t" (map show y) ++ "\n}" ++
+      (case z of
+        Just vals ->
+          " else {\n\t" ++ intercalate "\n\t" (map show vals) ++ "\n}"
+        Nothing -> "")
   show (BOp  o) = o
   show (BNum n) = show n
   show (BErr e) = "error: " ++ e
@@ -36,11 +46,11 @@ instance Floating Number where
     tanh x =  sinh x / cosh x
 
 instance Num Number where
-  (BInt x) + (BInt y) = BInt $ x * y
+  (BInt x) + (BInt y) = BInt $ x + y
-  (BFloat x) + (BFloat y) = BFloat $ x * y
+  (BFloat x) + (BFloat y) = BFloat $ x + y
-  (BInt x) + (BFloat y) = BFloat $ fromIntegral x * y
+  (BInt x) + (BFloat y) = BFloat $ fromIntegral x + y
-  (BFloat x) + (BInt y) = BFloat $ x * fromIntegral y
+  (BFloat x) + (BInt y) = BFloat $ x + fromIntegral y
-  (BInt x) * (BInt y) = BInt $ x * y
+  (BInt x) * (BInt y) = BInt $ x + y
   (BFloat x) * (BFloat y) = BFloat $ x * y
   (BInt x) * (BFloat y) = BFloat $ fromIntegral x * y
   (BFloat x) * (BInt y) = BFloat $ x * fromIntegral y