Equality operator

1 files changed, 13 insertions, 2 deletions

diff --git a/VM.hs b/VM.hs
index b3b19e4..12ccf60 100644
--- a/VM.hs
+++ b/VM.hs
@@ -100,6 +100,7 @@ assignRef _ ref _ = error $ "VM: Unexpected ref " ++ show ref ++ " assigned"
 vmRunBuiltin :: Name -> [RunValue] -> IO RunValue
 -- vmRunBuiltin name args | trace (name ++ " " ++ show args) False = undefined
 vmRunBuiltin "print" as = putStrLn (intercalate ", " (map printshow as)) >> return (RVList [])
+vmRunBuiltin "=" [a, b] = return (if equalOp a b then RVNum 1 else RVNum 0)
 vmRunBuiltin "<=" [RVNum a, RVNum b] = return (RVNum (fromEnum (a <= b)))
 vmRunBuiltin "+" [RVNum a, RVNum b] = return (RVNum (a + b))
 vmRunBuiltin "-" [RVNum a, RVNum b] = return (RVNum (a - b))
@@ -112,11 +113,21 @@ vmRunBuiltin "cdr" [RVList l] = case l of
 vmRunBuiltin "list" values = return (RVList values)
 vmRunBuiltin name args = error (name ++ " " ++ show args)
 
+equalOp :: RunValue -> RunValue -> Bool
+equalOp (RVClosure _ _) _ = error "Cannot compare closures in '='"
+equalOp _ (RVClosure _ _) = error "Cannot compare closures in '='"
+equalOp (RVList vs) (RVList ws) = length vs == length ws && all id (zipWith equalOp vs ws)
+equalOp (RVNum a) (RVNum b) = a == b
+equalOp (RVString s) (RVString t) = s == t
+equalOp (RVQuoted v) (RVQuoted w) = equalOp v w
+equalOp (RVName n) (RVName m) = n == m
+equalOp _ _ = False
+
 printshow :: RunValue -> String
 printshow (RVString str) = str
-printshow (RVList values) = show values
+printshow (RVList values) = "[" ++ intercalate "," (map printshow values) ++ "]"
 printshow (RVNum i) = show i
-printshow (RVQuoted value) = '\'' : show value
+printshow (RVQuoted value) = '\'' : printshow value
 printshow (RVClosure _ _) = "[closure]"
 printshow (RVName name) = name