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{-| PyValueInstances contains instances for the 'PyValue' typeclass.

The typeclass 'PyValue' converts Haskell values to Python values.

This module contains instances of this typeclass for several generic

types.  These instances are used in the Haskell to Python generation

of opcodes and constants, for example.

-}

{-

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.

-}

{-# LANGUAGE ExistentialQuantification #-}

{-# LANGUAGE FlexibleInstances, OverlappingInstances,

             TypeSynonymInstances, IncoherentInstances #-}

module Ganeti.PyValueInstances where

import Data.List (intercalate)

import Data.Map (Map)

import qualified Data.Map as Map

import qualified Data.Set as Set (toList)

import Ganeti.BasicTypes

-- * PyValue represents data types convertible to Python

-- | Converts Haskell values into Python values

--

-- This is necessary for the default values of opcode parameters and

-- return values.  For example, if a default value or return type is a

-- Data.Map, then it must be shown as a Python dictioanry.

class PyValue a where

  showValue :: a -> String

instance PyValue Bool where

  showValue = show

instance PyValue Int where

  showValue = show

instance PyValue Integer where

  showValue = show

instance PyValue Double where

  showValue = show

instance PyValue Char where

  showValue = show

instance (PyValue a, PyValue b) => PyValue (a, b) where

  showValue (x, y) = "(" ++ showValue x ++ "," ++ showValue y ++ ")"

instance (PyValue a, PyValue b, PyValue c) => PyValue (a, b, c) where

  showValue (x, y, z) =

    "(" ++

    showValue x ++ "," ++

    showValue y ++ "," ++

    showValue z ++

    ")"

instance PyValue String where

  showValue = show

instance PyValue a => PyValue [a] where

  showValue xs = "[" ++ intercalate "," (map showValue xs) ++ "]"

instance (PyValue k, PyValue a) => PyValue (Map k a) where

  showValue mp =

    "{" ++ intercalate ", " (map showPair (Map.assocs mp)) ++ "}"

    where showPair (k, x) = showValue k ++ ":" ++ showValue x

instance PyValue a => PyValue (ListSet a) where

  showValue = showValue . Set.toList . unListSet

-- * PyValue represents an unspecified value convertible to Python

-- | Encapsulates Python default values

data PyValueEx = forall a. PyValue a => PyValueEx a

instance PyValue PyValueEx where

  showValue (PyValueEx x) = showValue x