-- | Helper for 'niceSort'. Computes the key element for a given string.
extractKey :: [Either Integer String]  -- ^ Current (partial) key, reversed
           -> String                   -- ^ Remaining string
           -> ([Either Integer String], String)
extractKey ek [] = (reverse ek, [])
extractKey :: [Either Integer String]  -- ^ Current (partial) key, reversed
           -> String                   -- ^ Remaining string
           -> ([Either Integer String], String)
extractKey ek [] = (reverse ek, [])
extractKey ek [] = (reverse ek, [])