Synnefo » snf-ganeti » ganeti-local

{-| Some common types.

-}

module Ganeti.HTools.Types

    ( Idx

    , Ndx

    , NameAssoc

    , Result(..)

    , Element(..)

    ) where

-- | The instance index type.

type Idx = Int

-- | The node index type.

type Ndx = Int

-- | The type used to hold name-to-idx mappings.

type NameAssoc = [(String, Int)]

{-|

This is similar to the JSON library Result type - *very* similar, but

we want to use it in multiple places, so we abstract it into a

mini-library here

-}

data Result a

    = Bad String

    | Ok a

    deriving (Show)

instance Monad Result where

    (>>=) (Bad x) _ = Bad x

    (>>=) (Ok x) fn = fn x

    return = Ok

    fail = Bad

-- | A generic class for items that have updateable names and indices.

class Element a where

    -- | Returns the name of the element

    nameOf  :: a -> String

    -- | Returns the index of the element

    idxOf   :: a -> Int

    -- | Updates the name of the element

    setName :: a -> String -> a

    -- | Updates the index of the element

    setIdx  :: a -> Int -> a