root / Ganeti / HTools / Utils.hs @ d85a0a0f
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{-| Utility functions -} |
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module Ganeti.HTools.Utils |
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( |
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debug |
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, sepSplit |
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, varianceCoeff |
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, commaJoin |
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, readEitherString |
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, loadJSArray |
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, fromObj |
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, asJSObject |
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, asObjectList |
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, fromJResult |
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) where |
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import Data.List |
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import Control.Monad |
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import System |
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import System.IO |
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import qualified Text.JSON as J |
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import Text.Printf (printf) |
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import Ganeti.HTools.Types |
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import Debug.Trace |
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-- * Debug functions |
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-- | To be used only for debugging, breaks referential integrity. |
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debug :: Show a => a -> a |
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debug x = trace (show x) x |
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-- * Miscelaneous |
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-- | Comma-join a string list. |
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commaJoin :: [String] -> String |
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commaJoin = intercalate "," |
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-- | Split a string on a separator and return an array. |
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sepSplit :: Char -> String -> [String] |
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sepSplit sep s |
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| x == "" && xs == [] = [] |
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| xs == [] = [x] |
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| ys == [] = x:"":[] |
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| otherwise = x:(sepSplit sep ys) |
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where (x, xs) = break (== sep) s |
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ys = drop 1 xs |
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-- | Partial application of sepSplit to @'.'@ |
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commaSplit :: String -> [String] |
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commaSplit = sepSplit ',' |
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-- * Mathematical functions |
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-- Simple and slow statistical functions, please replace with better versions |
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-- | Mean value of a list. |
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meanValue :: Floating a => [a] -> a |
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meanValue lst = (sum lst) / (fromIntegral $ length lst) |
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-- | Standard deviation. |
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stdDev :: Floating a => [a] -> a |
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stdDev lst = |
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let mv = meanValue lst |
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square = (^ (2::Int)) -- silences "defaulting the constraint..." |
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av = sum $ map square $ map (\e -> e - mv) lst |
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bv = sqrt (av / (fromIntegral $ length lst)) |
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in bv |
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-- | Coefficient of variation. |
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varianceCoeff :: Floating a => [a] -> a |
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varianceCoeff lst = (stdDev lst) / (fromIntegral $ length lst) |
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-- * JSON-related functions |
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-- | Converts a JSON Result into a monadic value. |
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fromJResult :: Monad m => J.Result a -> m a |
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fromJResult (J.Error x) = fail x |
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fromJResult (J.Ok x) = return x |
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-- | Tries to read a string from a JSON value. |
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-- |
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-- In case the value was not a string, we fail the read (in the |
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-- context of the current monad. |
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readEitherString :: (Monad m) => J.JSValue -> m String |
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readEitherString v = |
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case v of |
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J.JSString s -> return $ J.fromJSString s |
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_ -> fail "Wrong JSON type" |
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-- | Converts a JSON message into an array of JSON objects. |
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loadJSArray :: (Monad m) => String -> m [J.JSObject J.JSValue] |
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loadJSArray s = fromJResult $ J.decodeStrict s |
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-- | Reads a the value of a key in a JSON object. |
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fromObj :: (J.JSON a, Monad m) => String -> J.JSObject J.JSValue -> m a |
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fromObj k o = |
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case lookup k (J.fromJSObject o) of |
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Nothing -> fail $ printf "key '%s' not found in %s" k (show o) |
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Just val -> fromJResult $ J.readJSON val |
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-- | Converts a JSON value into a JSON object. |
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asJSObject :: (Monad m) => J.JSValue -> m (J.JSObject J.JSValue) |
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asJSObject (J.JSObject a) = return a |
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asJSObject _ = fail "not an object" |
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-- | Coneverts a list of JSON values into a list of JSON objects. |
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asObjectList :: (Monad m) => [J.JSValue] -> m [J.JSObject J.JSValue] |
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asObjectList = sequence . map asJSObject |