context-free-grammar-0.1.1: src/Data/Cfg/FixedPoint.hs

-- | The iterative fixed-point function.
module Data.Cfg.FixedPoint
  ( fixedPoint
  ) where

-- | Given a function and an initial value, find the fixed point of
-- the function.
fixedPoint :: Eq a => (a -> a) -> a -> a
fixedPoint f a = go $ iterate f a
  where
    go as@(a':a'':_) =
      if a' == a''
        then a'
        else go $ tail as
    go _ = error "fixedPoint: impossible"