module Operators where

data Op =
  Op Int Fixity
  deriving (Show, Eq)

data ArgKind
  = X
  | Y
  deriving (Show, Eq)

data Fixity
  = Infix ArgKind ArgKind
  | Prefix ArgKind
  | Suffix ArgKind
  deriving (Show, Eq)

isPrefix (Prefix _) = True
isPrefix _ = False

numArgs :: Op -> Int
numArgs (Op _ f) = go f
  where
    go (Infix _ _) = 2
    go _ = 1

type Ops = [(String, Op)]

argKind :: Char -> Maybe ArgKind
argKind 'x' = Just X
argKind 'y' = Just Y
argKind _ = Nothing

fixity :: String -> Maybe Fixity
fixity [l, 'f', r] = Infix <$> argKind l <*> argKind r
fixity ['f', x] = Prefix <$> argKind x
fixity [x, 'f'] = Suffix <$> argKind x
fixity _ = Nothing

xfx, xfy, yfx, fx, fy, xf, yf :: String -> Int -> (String, Op)
xfx o p = (o, Op p (Infix X X))

xfy o p = (o, Op p (Infix X Y))

yfx o p = (o, Op p (Infix Y X))

fx o p = (o, Op p (Prefix X))

fy o p = (o, Op p (Prefix Y))

xf o p = (o, Op p (Suffix X))

yf o p = (o, Op p (Suffix Y))