root / Ganeti / HTools / Utils.hs @ c6484f0b
History | View | Annotate | Download (3.6 kB)
1 |
{-| Utility functions -} |
---|---|
2 |
|
3 |
{- |
4 |
|
5 |
Copyright (C) 2009 Google Inc. |
6 |
|
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. |
11 |
|
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. |
16 |
|
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 |
20 |
02110-1301, USA. |
21 |
|
22 |
-} |
23 |
|
24 |
module Ganeti.HTools.Utils |
25 |
( |
26 |
debug |
27 |
, sepSplit |
28 |
, fst3 |
29 |
, varianceCoeff |
30 |
, commaJoin |
31 |
, readEitherString |
32 |
, loadJSArray |
33 |
, fromObj |
34 |
, asJSObject |
35 |
, asObjectList |
36 |
, fromJResult |
37 |
) where |
38 |
|
39 |
import Data.List |
40 |
import Control.Monad |
41 |
import qualified Text.JSON as J |
42 |
import Text.Printf (printf) |
43 |
|
44 |
import Debug.Trace |
45 |
|
46 |
-- * Debug functions |
47 |
|
48 |
-- | To be used only for debugging, breaks referential integrity. |
49 |
debug :: Show a => a -> a |
50 |
debug x = trace (show x) x |
51 |
|
52 |
-- * Miscelaneous |
53 |
|
54 |
-- | Comma-join a string list. |
55 |
commaJoin :: [String] -> String |
56 |
commaJoin = intercalate "," |
57 |
|
58 |
-- | Split a string on a separator and return an array. |
59 |
sepSplit :: Char -> String -> [String] |
60 |
sepSplit sep s |
61 |
| x == "" && xs == [] = [] |
62 |
| xs == [] = [x] |
63 |
| ys == [] = x:"":[] |
64 |
| otherwise = x:(sepSplit sep ys) |
65 |
where (x, xs) = break (== sep) s |
66 |
ys = drop 1 xs |
67 |
|
68 |
-- | Simple version of 'fst' for a triple |
69 |
fst3 :: (a, b, c) -> a |
70 |
fst3 (a, _, _) = a |
71 |
|
72 |
-- * Mathematical functions |
73 |
|
74 |
-- Simple and slow statistical functions, please replace with better versions |
75 |
|
76 |
-- | Mean value of a list. |
77 |
meanValue :: Floating a => [a] -> a |
78 |
meanValue lst = (sum lst) / (fromIntegral $ length lst) |
79 |
|
80 |
-- | Squaring function |
81 |
square :: (Num a) => a -> a |
82 |
square = (^ 2) |
83 |
|
84 |
-- | Standard deviation. |
85 |
stdDev :: Floating a => [a] -> a |
86 |
stdDev lst = |
87 |
let mv = meanValue lst |
88 |
av = sum $ map square $ map (\e -> e - mv) lst |
89 |
bv = sqrt (av / (fromIntegral $ length lst)) |
90 |
in bv |
91 |
|
92 |
-- | Coefficient of variation. |
93 |
varianceCoeff :: Floating a => [a] -> a |
94 |
varianceCoeff lst = (stdDev lst) / (fromIntegral $ length lst) |
95 |
|
96 |
-- * JSON-related functions |
97 |
|
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 |
102 |
|
103 |
-- | Tries to read a string from a JSON value. |
104 |
-- |
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 |
108 |
readEitherString v = |
109 |
case v of |
110 |
J.JSString s -> return $ J.fromJSString s |
111 |
_ -> fail "Wrong JSON type" |
112 |
|
113 |
-- | Converts a JSON message into an array of JSON objects. |
114 |
loadJSArray :: (Monad m) => String -> m [J.JSObject J.JSValue] |
115 |
loadJSArray s = fromJResult $ J.decodeStrict s |
116 |
|
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 |
119 |
fromObj k o = |
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 |
123 |
|
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" |
128 |
|
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 = sequence . map asJSObject |