1 {-| Utility functions -}
5 Copyright (C) 2009 Google Inc.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
24 module Ganeti.HTools.Utils
41 import qualified Text.JSON as J
42 import Text.Printf (printf)
48 -- | To be used only for debugging, breaks referential integrity.
49 debug :: Show a => a -> a
50 debug x = trace (show x) x
54 -- | Comma-join a string list.
55 commaJoin :: [String] -> String
56 commaJoin = intercalate ","
58 -- | Split a string on a separator and return an array.
59 sepSplit :: Char -> String -> [String]
61 | x == "" && xs == [] = []
64 | otherwise = x:sepSplit sep ys
65 where (x, xs) = break (== sep) s
68 -- | Simple version of 'fst' for a triple
69 fst3 :: (a, b, c) -> a
72 -- * Mathematical functions
74 -- Simple and slow statistical functions, please replace with better versions
76 -- | Mean value of a list.
77 meanValue :: Floating a => [a] -> a
78 meanValue lst = sum lst / fromIntegral (length lst)
80 -- | Squaring function
81 square :: (Num a) => a -> a
84 -- | Standard deviation.
85 stdDev :: Floating a => [a] -> a
87 let mv = meanValue lst
88 av = sum $ map (square . (\e -> e - mv)) lst
89 bv = sqrt (av / fromIntegral (length lst))
92 -- | Coefficient of variation.
93 varianceCoeff :: Floating a => [a] -> a
94 varianceCoeff lst = stdDev lst / fromIntegral (length lst)
96 -- * JSON-related functions
98 -- | Converts a JSON Result into a monadic value.
99 fromJResult :: Monad m => J.Result a -> m a
100 fromJResult (J.Error x) = fail x
101 fromJResult (J.Ok x) = return x
103 -- | Tries to read a string from a JSON value.
105 -- In case the value was not a string, we fail the read (in the
106 -- context of the current monad.
107 readEitherString :: (Monad m) => J.JSValue -> m String
110 J.JSString s -> return $ J.fromJSString s
111 _ -> fail "Wrong JSON type"
113 -- | Converts a JSON message into an array of JSON objects.
114 loadJSArray :: (Monad m) => String -> m [J.JSObject J.JSValue]
115 loadJSArray = fromJResult . J.decodeStrict
117 -- | Reads a the value of a key in a JSON object.
118 fromObj :: (J.JSON a, Monad m) => String -> J.JSObject J.JSValue -> m a
120 case lookup k (J.fromJSObject o) of
121 Nothing -> fail $ printf "key '%s' not found in %s" k (show o)
122 Just val -> fromJResult $ J.readJSON val
124 -- | Converts a JSON value into a JSON object.
125 asJSObject :: (Monad m) => J.JSValue -> m (J.JSObject J.JSValue)
126 asJSObject (J.JSObject a) = return a
127 asJSObject _ = fail "not an object"
129 -- | Coneverts a list of JSON values into a list of JSON objects.
130 asObjectList :: (Monad m) => [J.JSValue] -> m [J.JSObject J.JSValue]
131 asObjectList = mapM asJSObject