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{-| ConstantUtils contains the helper functions for constants

This module cannot be merged with 'Ganeti.Utils' because it would

create a circular dependency if imported, for example, from

'Ganeti.Constants'.

-}

{-

Copyright (C) 2013 Google Inc.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.

-}

module Ganeti.ConstantUtils where

import Data.Set (Set)

import qualified Data.Set as Set (fromList, toList)

import Ganeti.THH (PyValue(..))

import Ganeti.PyValueInstances ()

-- | FrozenSet wraps a Haskell 'Set'

--

-- See 'PyValue' instance for 'FrozenSet'.

newtype FrozenSet a = FrozenSet { unFrozenSet :: Set a }

  deriving (Show)

-- | Converts a Haskell 'Set' into a Python 'frozenset'

--

-- This instance was supposed to be for 'Set' instead of 'FrozenSet'.

-- However, 'ghc-6.12.1' seems to be crashing with 'segmentation

-- fault' due to the presence of more than one instance of 'Set',

-- namely, this one and the one in 'Ganeti.OpCodes'.  For this reason,

-- we wrap 'Set' into 'FrozenSet'.

instance PyValue a => PyValue (FrozenSet a) where

  showValue s = "frozenset(" ++ showValue (Set.toList (unFrozenSet s)) ++ ")"

mkSet :: Ord a => [a] -> FrozenSet a

mkSet = FrozenSet . Set.fromList