Carriage/Carriage.hs

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Quick and dirty implementation of Carriage in Haskell. Program might not explode under every condition it is supposed to explode (but please do consider every error to be an explosion, not just BOOM). Runs the two examples given in the article.

 explode = error "BOOM"
 
 data Elem = Int Integer
           | Fn ([Elem] -> [Elem])
           | Sym Char
 instance Show Elem where
     show (Int i) = show i
     show (Fn _)  = "<fn>"
     show (Sym c) = show c
  
 pop (e:s) = (e, s)
 push s e = (e:s)
 
 pick 0 ((Sym _):_) = explode
 pick 0 (e:_) = e
 pick n (_:s) = pick (n-1) s
 
 slice _ 0 _ = []
 slice p k s = slice' p (reverse s)
     where
         slice' 0 s = take (fromIntegral k) s
         slice' n (_:s) = slice' (n-1) s
 
 ci " " = id
 ci "1" = \s -> push s $ Int 1
 ci "$" = snd . pop
 ci "#" = \s -> push s $ Int $ fromIntegral $ length s
 ci "~" = (\s ->
     let
         (Int a, s') = pop(s)
     in
         push s' $ pick a s')
 ci "\\" = (\s ->
     let
         (a, s') = pop(s)
         (b, s'') = pop(s')
     in
         push (push s'' a) b)
 ci "+" = (\s ->
     let
         (Int a, s') = pop(s)
         (Int b, s'') = pop(s')
     in
         push s'' $ Int (a + b))
 ci "-" = (\s ->
     let
         (Int a, s') = pop(s)
         (Int b, s'') = pop(s')
     in
         push s'' $ Int (b - a))
 ci "@" = (\s ->
     let
         (Int k, s') = pop(s)
         (Int p, s'') = pop(s')
         fn = ci $ map (\(Sym c) -> c) $ slice p k s''
     in
         push s'' (Fn fn))
 ci "!" = \s -> let (Fn f, s') = pop(s) in f s'
 ci [] = id
 ci [_] = explode
 ci (sym:rest) = \x -> (ci rest) ((ci [sym]) x)
 
 di = reverse . map (\x -> Sym x) . filter (\x -> x /= ' ')
 
 run prog = (ci prog) (di prog)
 

See also

• Carriage
• Carriage/carriage.ml