Some binary magic

1 files changed, 11 insertions, 13 deletions

diff --git a/src/Helper.hs b/src/Helper.hs
index 57fb9f4..60941be 100644
--- a/src/Helper.hs
+++ b/src/Helper.hs
@@ -3,9 +3,8 @@ module Helper where
 import           Control.Monad.State
 import           Text.Parsec             hiding ( State )
 
-data Error = SyntaxError ParseError | UndeclaredFunction String | DuplicateFunction String | InvalidIndex Int | FatalError String
+data Error = UndeclaredFunction String | DuplicateFunction String | InvalidIndex Int | FatalError String
 instance Show Error where
-  show (SyntaxError        err) = show err
   show (UndeclaredFunction err) = "ERROR: undeclared function " <> show err
   show (DuplicateFunction  err) = "ERROR: duplicate function " <> show err
   show (InvalidIndex       err) = "ERROR: invalid index " <> show err
@@ -14,7 +13,7 @@ type Failable = Either Error
 
 data Expression = Bruijn Int | Variable String | Abstraction Expression | Application Expression Expression
   deriving (Ord, Eq)
-data Instruction = Define String Expression | Evaluate Expression | Comment String | Load String | Test Expression Expression
+data Instruction = Define String Expression | Evaluate Expression | Comment String | Import String | Test Expression Expression
   deriving (Show)
 instance Show Expression where
   show (Bruijn      x        ) = show x
@@ -25,24 +24,23 @@ instance Show Expression where
 type Environment = [(String, Expression)]
 type Program = State Environment
 
--- Dec to Bal3 in Bruijn encoding: reversed application with 1=>0; 0=>1; T=>2; end=>3
--- e.g. 0=0=[[[[3]]]]; 2=1T=[[[[2 (0 3)]]]] -5=T11=[[[[0 (0 (2 3))]]]]
-decimalToTernary :: Integer -> Expression
-decimalToTernary n =
-  Abstraction $ Abstraction $ Abstraction $ Abstraction $ gen n
+decimalToBinary :: Integer -> Expression
+decimalToBinary n = Abstraction $ Abstraction $ Abstraction $ Abstraction $ gen
+  n
  where -- TODO: Consider switching 0 and 1 for better readability
   fix 0 = 1
   fix 1 = 0
-  fix 2 = 2
   gen 0 = Bruijn 3
-  gen n = Application (Bruijn $ fix $ mod n 3) (gen $ div (n + 1) 3)
+  gen 1 = Application (Bruijn 0) (gen 0)
+  gen n | n < 0     = Application (Bruijn 2) (gen (-n))
+        | otherwise = Application (Bruijn $ fix $ mod n 2) (gen $ div n 2)
 
-ternaryToDecimal :: Expression -> Integer
-ternaryToDecimal exp = sum $ zipWith (*) (resolve exp) (iterate (* 3) 1)
+binaryToDecimal :: Expression -> Integer
+binaryToDecimal exp = sum $ zipWith (*) (resolve exp) (iterate (* 2) 1)
  where
   multiplier (Bruijn 0) = 1
   multiplier (Bruijn 1) = 0
-  multiplier (Bruijn 2) = (-1)
+  multiplier (Bruijn 2) = -1 -- TODO
   resolve' (Application x@(Bruijn _) (Bruijn 3)) = [multiplier x]
   resolve' (Application fst@(Bruijn _) rst@(Application _ _)) =
     (multiplier fst) : (resolve' rst)