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Clean up function names

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Also create separate showExpression function
This commit is contained in:
Joscha 2017-11-25 20:06:15 +00:00
parent fec6dcb7cf
commit 46d74f73f2
1 changed files with 46 additions and 34 deletions
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60
lambda.hs
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@ -1,3 +1,10 @@
-- module Lambda
-- ( Expression
-- , showExpression
-- , maybeParseExpression
-- , evaluateExpression
-- ) where
import Control.Monad
import Data.List
import Data.Maybe
@ -11,6 +18,24 @@ data Expression s = ESymbol s
| EReference Int
| EExpr (Expression s) (Expression s)
| ELambda s (Expression s)
deriving (Show)
instance (Eq s) => Eq (Expression s) where
(ESymbol a) == (ESymbol b) = a == b
(EReference a) == (EReference b) = a == b
(EExpr a b) == (EExpr c d) = a == c && b == d
(ELambda _ a) == (ELambda _ b) = a == b
_ == _ = False
instance Functor Expression where
fmap f (EReference n) = EReference n
fmap f (ESymbol a) = ESymbol (f a)
fmap f (ELambda s e) = ELambda (f s) (fmap f e)
fmap f (EExpr a b) = EExpr (fmap f a) (fmap f b)
{-
- Displaying expressions
-}
-- list of names -> name -> unique name
-- Find a unique name not in the list of names.
@ -32,14 +57,14 @@ renameUniquely = rename_ []
rename_ c (ELambda s e) = let name = makeUnique c . show $ s
in ELambda name (rename_ (name : c) e)
instance (Show s) => Show (Expression s) where
show = show_ [] . renameUniquely
-- show_ :: Expression String -> String
showExpression :: (Show s) => Bool -> Expression s -> String
showExpression unicode = show_ [] . renameUniquely
where show_ c (EReference n)
| n >= 0 && n < length c = c !! n
| otherwise = "ERR" -- TODO: Deal with errors properly?
show_ c (ESymbol s) = s
show_ c (ELambda s e) = "\\" ++ s ++ "." ++ show_ (s : c) e
show_ c (ELambda s e) = (if unicode then "λ" else "\\")
++ s ++ "." ++ show_ (s : c) e
show_ c (EExpr a@(ELambda _ _) b@(ELambda _ _)) = "(" ++ show_ c a ++ ") (" ++ show_ c b ++ ")"
show_ c (EExpr a@(ELambda _ _) b@(EExpr _ _)) = "(" ++ show_ c a ++ ") (" ++ show_ c b ++ ")"
show_ c (EExpr a@(ELambda _ _) b ) = "(" ++ show_ c a ++ ") " ++ show_ c b
@ -47,19 +72,6 @@ instance (Show s) => Show (Expression s) where
show_ c (EExpr a b@(EExpr _ _)) = show_ c a ++ " (" ++ show_ c b ++ ")"
show_ c (EExpr a b) = show_ c a ++ " " ++ show_ c b
instance (Eq s) => Eq (Expression s) where
(ESymbol a) == (ESymbol b) = a == b
(EReference a) == (EReference b) = a == b
(EExpr a b) == (EExpr c d) = a == c && b == d
(ELambda _ a) == (ELambda _ b) = a == b
_ == _ = False
instance Functor Expression where
fmap f (EReference n) = EReference n
fmap f (ESymbol a) = ESymbol (f a)
fmap f (ELambda s e) = ELambda (f s) (fmap f e)
fmap f (EExpr a b) = EExpr (fmap f a) (fmap f b)
{-
- Evaluating expressions
-}
@ -85,8 +97,8 @@ takeWhileUnique l = map fst
$ takeWhile (\a -> not $ fst a `elem` snd a)
$ zip l (inits l)
evaluate :: (Eq s) => Expression s -> [Expression s]
evaluate = takeWhileUnique . iterate apply
evaluateExpression :: (Eq s) => Expression s -> [Expression s]
evaluateExpression = takeWhileUnique . iterate apply
{-
- Parsing expressions
@ -174,14 +186,14 @@ instance Eq StrSymbol where
linewise :: (String -> String) -> String -> String
linewise f = unlines . map f . lines
evaluateExpression :: String -> String
evaluateExpression s =
evaluate :: String -> String
evaluate s =
let result = return
. map show
. evaluate
. map (showExpression True)
. evaluateExpression
. fmap StrSymbol
l = fromMaybe ["Error: Could not parse expression."]
$ maybeParseExpression s >>= result
in unlines l
main = interact $ linewise evaluateExpression
main = interact $ linewise evaluate