Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Browse files

Initial HFlags release.

  • Loading branch information...
commit b04c581afdd0d20c93cd37e449efdd3443652336 1 parent 1ebf4f1
@errge errge authored
View
202 COPYING
@@ -0,0 +1,202 @@
+
+ Apache License
+ Version 2.0, January 2004
+ http://www.apache.org/licenses/
+
+ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+ 1. Definitions.
+
+ "License" shall mean the terms and conditions for use, reproduction,
+ and distribution as defined by Sections 1 through 9 of this document.
+
+ "Licensor" shall mean the copyright owner or entity authorized by
+ the copyright owner that is granting the License.
+
+ "Legal Entity" shall mean the union of the acting entity and all
+ other entities that control, are controlled by, or are under common
+ control with that entity. For the purposes of this definition,
+ "control" means (i) the power, direct or indirect, to cause the
+ direction or management of such entity, whether by contract or
+ otherwise, or (ii) ownership of fifty percent (50%) or more of the
+ outstanding shares, or (iii) beneficial ownership of such entity.
+
+ "You" (or "Your") shall mean an individual or Legal Entity
+ exercising permissions granted by this License.
+
+ "Source" form shall mean the preferred form for making modifications,
+ including but not limited to software source code, documentation
+ source, and configuration files.
+
+ "Object" form shall mean any form resulting from mechanical
+ transformation or translation of a Source form, including but
+ not limited to compiled object code, generated documentation,
+ and conversions to other media types.
+
+ "Work" shall mean the work of authorship, whether in Source or
+ Object form, made available under the License, as indicated by a
+ copyright notice that is included in or attached to the work
+ (an example is provided in the Appendix below).
+
+ "Derivative Works" shall mean any work, whether in Source or Object
+ form, that is based on (or derived from) the Work and for which the
+ editorial revisions, annotations, elaborations, or other modifications
+ represent, as a whole, an original work of authorship. For the purposes
+ of this License, Derivative Works shall not include works that remain
+ separable from, or merely link (or bind by name) to the interfaces of,
+ the Work and Derivative Works thereof.
+
+ "Contribution" shall mean any work of authorship, including
+ the original version of the Work and any modifications or additions
+ to that Work or Derivative Works thereof, that is intentionally
+ submitted to Licensor for inclusion in the Work by the copyright owner
+ or by an individual or Legal Entity authorized to submit on behalf of
+ the copyright owner. For the purposes of this definition, "submitted"
+ means any form of electronic, verbal, or written communication sent
+ to the Licensor or its representatives, including but not limited to
+ communication on electronic mailing lists, source code control systems,
+ and issue tracking systems that are managed by, or on behalf of, the
+ Licensor for the purpose of discussing and improving the Work, but
+ excluding communication that is conspicuously marked or otherwise
+ designated in writing by the copyright owner as "Not a Contribution."
+
+ "Contributor" shall mean Licensor and any individual or Legal Entity
+ on behalf of whom a Contribution has been received by Licensor and
+ subsequently incorporated within the Work.
+
+ 2. Grant of Copyright License. Subject to the terms and conditions of
+ this License, each Contributor hereby grants to You a perpetual,
+ worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+ copyright license to reproduce, prepare Derivative Works of,
+ publicly display, publicly perform, sublicense, and distribute the
+ Work and such Derivative Works in Source or Object form.
+
+ 3. Grant of Patent License. Subject to the terms and conditions of
+ this License, each Contributor hereby grants to You a perpetual,
+ worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+ (except as stated in this section) patent license to make, have made,
+ use, offer to sell, sell, import, and otherwise transfer the Work,
+ where such license applies only to those patent claims licensable
+ by such Contributor that are necessarily infringed by their
+ Contribution(s) alone or by combination of their Contribution(s)
+ with the Work to which such Contribution(s) was submitted. If You
+ institute patent litigation against any entity (including a
+ cross-claim or counterclaim in a lawsuit) alleging that the Work
+ or a Contribution incorporated within the Work constitutes direct
+ or contributory patent infringement, then any patent licenses
+ granted to You under this License for that Work shall terminate
+ as of the date such litigation is filed.
+
+ 4. Redistribution. You may reproduce and distribute copies of the
+ Work or Derivative Works thereof in any medium, with or without
+ modifications, and in Source or Object form, provided that You
+ meet the following conditions:
+
+ (a) You must give any other recipients of the Work or
+ Derivative Works a copy of this License; and
+
+ (b) You must cause any modified files to carry prominent notices
+ stating that You changed the files; and
+
+ (c) You must retain, in the Source form of any Derivative Works
+ that You distribute, all copyright, patent, trademark, and
+ attribution notices from the Source form of the Work,
+ excluding those notices that do not pertain to any part of
+ the Derivative Works; and
+
+ (d) If the Work includes a "NOTICE" text file as part of its
+ distribution, then any Derivative Works that You distribute must
+ include a readable copy of the attribution notices contained
+ within such NOTICE file, excluding those notices that do not
+ pertain to any part of the Derivative Works, in at least one
+ of the following places: within a NOTICE text file distributed
+ as part of the Derivative Works; within the Source form or
+ documentation, if provided along with the Derivative Works; or,
+ within a display generated by the Derivative Works, if and
+ wherever such third-party notices normally appear. The contents
+ of the NOTICE file are for informational purposes only and
+ do not modify the License. You may add Your own attribution
+ notices within Derivative Works that You distribute, alongside
+ or as an addendum to the NOTICE text from the Work, provided
+ that such additional attribution notices cannot be construed
+ as modifying the License.
+
+ You may add Your own copyright statement to Your modifications and
+ may provide additional or different license terms and conditions
+ for use, reproduction, or distribution of Your modifications, or
+ for any such Derivative Works as a whole, provided Your use,
+ reproduction, and distribution of the Work otherwise complies with
+ the conditions stated in this License.
+
+ 5. Submission of Contributions. Unless You explicitly state otherwise,
+ any Contribution intentionally submitted for inclusion in the Work
+ by You to the Licensor shall be under the terms and conditions of
+ this License, without any additional terms or conditions.
+ Notwithstanding the above, nothing herein shall supersede or modify
+ the terms of any separate license agreement you may have executed
+ with Licensor regarding such Contributions.
+
+ 6. Trademarks. This License does not grant permission to use the trade
+ names, trademarks, service marks, or product names of the Licensor,
+ except as required for reasonable and customary use in describing the
+ origin of the Work and reproducing the content of the NOTICE file.
+
+ 7. Disclaimer of Warranty. Unless required by applicable law or
+ agreed to in writing, Licensor provides the Work (and each
+ Contributor provides its Contributions) on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ implied, including, without limitation, any warranties or conditions
+ of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+ PARTICULAR PURPOSE. You are solely responsible for determining the
+ appropriateness of using or redistributing the Work and assume any
+ risks associated with Your exercise of permissions under this License.
+
+ 8. Limitation of Liability. In no event and under no legal theory,
+ whether in tort (including negligence), contract, or otherwise,
+ unless required by applicable law (such as deliberate and grossly
+ negligent acts) or agreed to in writing, shall any Contributor be
+ liable to You for damages, including any direct, indirect, special,
+ incidental, or consequential damages of any character arising as a
+ result of this License or out of the use or inability to use the
+ Work (including but not limited to damages for loss of goodwill,
+ work stoppage, computer failure or malfunction, or any and all
+ other commercial damages or losses), even if such Contributor
+ has been advised of the possibility of such damages.
+
+ 9. Accepting Warranty or Additional Liability. While redistributing
+ the Work or Derivative Works thereof, You may choose to offer,
+ and charge a fee for, acceptance of support, warranty, indemnity,
+ or other liability obligations and/or rights consistent with this
+ License. However, in accepting such obligations, You may act only
+ on Your own behalf and on Your sole responsibility, not on behalf
+ of any other Contributor, and only if You agree to indemnify,
+ defend, and hold each Contributor harmless for any liability
+ incurred by, or claims asserted against, such Contributor by reason
+ of your accepting any such warranty or additional liability.
+
+ END OF TERMS AND CONDITIONS
+
+ APPENDIX: How to apply the Apache License to your work.
+
+ To apply the Apache License to your work, attach the following
+ boilerplate notice, with the fields enclosed by brackets "[]"
+ replaced with your own identifying information. (Don't include
+ the brackets!) The text should be enclosed in the appropriate
+ comment syntax for the file format. We also recommend that a
+ file or class name and description of purpose be included on the
+ same "printed page" as the copyright notice for easier
+ identification within third-party archives.
+
+ Copyright [yyyy] [name of copyright owner]
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
View
320 HFlags.hs
@@ -0,0 +1,320 @@
+-- Copyright 2012 Google Inc. All Rights Reserved.
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+-- http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+--
+-- Authors: Mihaly Barasz <klao@google.com>, Gergely Risko <errge@google.com>
+
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TypeSynonymInstances #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE NamedFieldPuns #-}
+
+-- |
+-- Module: HFlags
+-- License: Apache 2.0
+--
+-- The @HFlags@ library supports easy definition of command line flags,
+-- reimplementing the ideas from Google's @gflags@
+-- (<http://code.google.com/p/gflags>).
+--
+-- Command line flags can be declared in any file at the toplevel,
+-- using 'defineFlag'. At runtime, the actual values are assigned to
+-- the toplevel @flags_name@ constants. Those can be used purely
+-- throughout the program.
+--
+-- At the beginning of the @main@ function, @$(initHFlags "program
+-- description")@ has to be called to initialize the flags. All flags
+-- will be initialized that are transitively reachable via imports
+-- from @main@. This means, that any Haskell package can easily
+-- define command line flags with @HFlags@. This feature is
+-- demonstrated by
+-- <http://github.com/errge/hflags/blob/master/examples/ImportExample.hs>.
+--
+-- A simple example (more in the
+-- <http://github.com/errge/hflags/tree/master/examples> directory):
+--
+-- > #!/usr/bin/env runhaskell
+-- >
+-- > {-# LANGUAGE TemplateHaskell #-}
+-- >
+-- > import HFlags
+-- >
+-- > defineFlag "name" "Indiana Jones" "Who to greet."
+-- > defineFlag "r:repeat" (3 + 4 :: Int) "Number of times to repeat the message."
+-- >
+-- > main = do s <- $(initHFlags "Simple program v0.1")
+-- > sequence_ $ replicate flags_repeat greet
+-- > where
+-- > greet = putStrLn $ "Hello " ++ flags_name ++ ", very nice to meet you!"
+--
+-- At @initHFlags@ time, the library also tries to gather flags out of
+-- environment variables. @HFLAGS_verbose=True@ is equivalent to
+-- specify --verbose=True. This environment feature only works with
+-- long options and the user has to specify a value even for Bools.
+
+module HFlags (
+ -- * Definition of flags
+ defineCustomFlag,
+ defineQQFlag,
+ FlagType(..),
+ -- * Initialization of flags at runtime
+ initHFlags) where
+
+-- TODOs:
+-- ?--no* for bools?
+-- --help should show the current value if it's different than the default value, so user can test command line args
+
+import Control.Exception
+import Control.Monad
+import Data.Char
+import Data.Function
+import Data.List
+import Data.IORef
+import Data.Maybe
+import qualified Data.Map as Map
+import Data.Map (Map, (!))
+import Language.Haskell.TH
+import System.Console.GetOpt
+import System.Environment
+import System.IO
+import System.IO.Unsafe
+import System.Exit
+
+import Prelude hiding (catch)
+
+-- | Data type for storing every property of a flag.
+data FlagData = FlagData
+ { fName :: String
+ , fShort :: Maybe Char
+ , fDefValue :: String
+ , fArgHelp :: String
+ , fDescription :: String
+ , fModuleName :: String
+ , fCheck :: IO () -- ^ function to evaluate in 'initFlags'
+ -- to force syntax check of the argument.
+ }
+
+-- | Every flag the program supports has to be defined through a new
+-- phantom datatype and the Flag instance of that datatype.
+--
+-- But users of the library shouldn't worry about this class or the
+-- implementation details behind these functions, just use the
+-- @defineFlag@ Template Haskell function for defining new flags.
+class Flag a where
+ getFlagData :: a -> FlagData
+
+-- | The most flexible way of defining a flag. For an example see
+-- <http://github.com/errge/hflags/blob/master/examples/ComplexExample.hs>.
+-- For most things 'defineFlag' should be enough instead.
+--
+-- The parameters:
+--
+-- * name of the flag (@l:long@ syntax if you want to have the short option @l@ for this flag),
+--
+-- * quasiquoted and type signed default value,
+--
+-- * help string for the argument,
+--
+-- * read function, quasiquoted,
+--
+-- * show function, quasiquoted,
+--
+-- * help string for the flag.
+defineCustomFlag :: String -> ExpQ -> String -> ExpQ -> ExpQ -> String -> Q [Dec]
+defineCustomFlag name' defQ argHelp readQ showQ description =
+ do (name, short) <- case () of
+ () | length name' == 0 -> fail "Flag's without names are not supported."
+ | length name' == 1 -> return (name', Just $ head name')
+ | length name' == 2 -> return (name', Nothing)
+ | name' !! 1 == ':' -> return (drop 2 name', Just $ head name')
+ | otherwise -> return (name', Nothing)
+ defE <- defQ
+ case defE of
+ SigE _ _ -> return ()
+ _ -> fail "Default value for defineCustomFlag has to be an explicitly typed expression, like (12 :: Int)"
+ moduleName <- fmap loc_module location
+ let accessorName = mkName $ "flags_" ++ name
+ let dataName = mkName $ "HFlag_" ++ name
+ dataDec <- return $ DataD [] dataName [] [] []
+ instanceDec <- instanceD
+ (return [])
+ (appT (conT ''Flag) (conT dataName))
+ [funD 'getFlagData [clause [wildP]
+ (normalB
+ [| FlagData
+ name
+ short
+ $(appE showQ defQ)
+ argHelp
+ description
+ moduleName
+ (evaluate $(varE accessorName) >> return ())
+ |]) []]]
+ flagPragmaDec <- return $ PragmaD $ InlineP accessorName $ InlineSpec False False Nothing
+ flagDec <- funD accessorName [clause [] (normalB [| case True of
+ True -> $(appE readQ [| lookupFlag name moduleName |])
+ False -> $(defQ) |]) []]
+ return [dataDec, instanceDec, flagPragmaDec, flagDec]
+
+-- | This just forwards to 'defineCustomFlag' with @[| read |]@ and
+-- @[| show |]@. Useful for flags where the type is not an instance
+-- of 'FlagType'. For examples, see
+-- <http://github.com/errge/hflags/blob/master/examples/ComplexExample.hs>.
+--
+-- The parameters:
+--
+-- * name of the flag (@l:long@ syntax if you want to have the short option @l@ for this flag),,
+--
+-- * quasiquoted and type signed default value,
+--
+-- * help string for the argument,
+--
+-- * help string for the flag.
+defineQQFlag :: String -> ExpQ -> String -> String -> Q [Dec]
+defineQQFlag name defQ argHelp description =
+ defineCustomFlag name defQ argHelp [| read |] [| show |] description
+
+-- | Class of types for which the easy 'defineFlag' syntax is supported.
+class FlagType t where
+ -- | The @defineFlag@ function defines a new flag.
+ --
+ -- The parameters:
+ --
+ -- * name of the flag (@l:long@ syntax if you want to have the short option @l@ for this flag),,
+ --
+ -- * default value,
+ --
+ -- * help string for the flag.
+ defineFlag :: String -> t -> String -> Q [Dec]
+
+boolShow :: Bool -> String
+boolShow True = "true"
+boolShow False = "false"
+
+boolRead :: String -> Bool
+boolRead = boolRead' . map toLower
+ where
+ boolRead' ('y':_) = True
+ boolRead' ('t':_) = True
+ boolRead' ('1':_) = True
+ boolRead' ('n':_) = False
+ boolRead' ('f':_) = False
+ boolRead' ('0':_) = False
+ boolRead' s = error $ "Unable to parse string as boolean: " ++ s
+
+instance FlagType Bool where
+ defineFlag n v = defineCustomFlag n [| v :: Bool |] "BOOL" [| boolRead |] [| boolShow |]
+
+instance FlagType Int where
+ defineFlag n v = defineQQFlag n [| v :: Int |] "INT"
+
+instance FlagType Integer where
+ defineFlag n v = defineQQFlag n [| v :: Integer |] "INTEGER"
+
+instance FlagType String where
+ defineFlag n v = defineCustomFlag n [| v :: String |] "STRING" [| id |] [| id |]
+
+instance FlagType Double where
+ defineFlag n v = defineQQFlag n (sigE (litE (RationalL (toRational v))) [t| Double |] ) "DOUBLE"
+
+-- | A global "IORef" for the communication between @initHFlags@ and
+-- @flag_*@. This is a map between flag name and current value.
+{-# NOINLINE globalHFlags #-}
+globalHFlags :: IORef (Maybe (Map String String))
+globalHFlags = unsafePerformIO $ newIORef Nothing
+
+lookupFlag :: String -> String -> String
+lookupFlag fName fModuleName = unsafePerformIO $ do
+ flags <- readIORef globalHFlags
+ case flags of
+ Just flagmap -> return $ flagmap ! fName
+ Nothing -> error $ "Flag " ++ fName ++ " (from module: " ++ fModuleName ++ ") used before calling initHFlags."
+
+-- | Initializes @globalHFlags@ and returns the non-option arguments.
+initFlags :: String -> [FlagData] -> [String] -> IO [String]
+initFlags progDescription flags args = do
+ doHelp
+ let (opts, nonopts, errs) | doUndefok = (\(a,b,_,c) -> (a,b,c)) $ getOpt' Permute getOptFlags args
+ | otherwise = getOpt Permute getOptFlags args
+ when (not $ null errs) $ do
+ mapM_ (hPutStrLn stderr) errs
+ exitFailure
+ let defaults = map (\FlagData { fName, fDefValue } -> (fName, fDefValue)) flags
+ env <- getEnvironment
+ let envDefaults = map (mapFst (fromJust . stripPrefix "HFLAGS_")) $ filter ((isPrefixOf "HFLAGS_") . fst) env
+ writeIORef globalHFlags $ Just $ Map.fromList $ defaults ++ envDefaults ++ opts
+ mapM_ forceFlag flags
+ return nonopts
+ where
+ mapFst f (a, b) = (f a, b)
+ helpOption = Option "h" ["help", "usage", "version"] (NoArg ("", "")) "Display help and version information."
+ doHelp = case getOpt Permute [helpOption] args of
+ ([], _, _) -> return ()
+ _ -> do putStrLn $ usageInfo (progDescription ++ "\n") (helpOption:undefokOption:getOptFlags)
+ exitFailure
+
+ undefokOption = Option "" ["undefok"] (NoArg ("", "")) "Whether to fail on unrecognized command line options."
+ doUndefok = case getOpt Permute [undefokOption] args of
+ ([], _, _) -> False
+ _ -> True
+
+ flagToGetOptArgDescr FlagData { fName, fArgHelp }
+ | fArgHelp == "BOOL" = OptArg (\a -> (fName, maybe "True" id a)) fArgHelp
+ | otherwise = ReqArg (\a -> (fName, a)) fArgHelp
+
+ -- compute GetOpt compatible [Option] structure from flags ([FlagData])
+ getOptFlags = flip map flags $ \flagData@(FlagData { fName, fShort, fDefValue, fDescription, fModuleName }) ->
+ Option (maybeToList fShort) [fName] (flagToGetOptArgDescr flagData)
+ (fDescription ++ " (default: " ++ fDefValue ++ ", from module: " ++ fModuleName ++ ")")
+
+ forceFlag FlagData { fName, fModuleName, fCheck } =
+ fCheck `catch`
+ (\e -> error $
+ "Error while parsing argument for flag: " ++ fName ++
+ ", value: " ++ lookupFlag fName fModuleName ++
+ ", error: " ++ show (e :: ErrorCall))
+
+-- | Has to be called from the main before doing anything else:
+--
+-- @
+-- main = do args <- $(initHFlags "Simple program v0.1")
+-- ...
+-- @
+--
+-- Internally, it uses Template Haskell trickery to gather all the
+-- instances of the Flag class and then generates a call to
+-- @initFlags@ with the appropriate data gathered together from those
+-- instances to a list.
+--
+-- Type after splicing is @IO [String]@.
+initHFlags :: String -> ExpQ -- IO [String]
+initHFlags progDescription = do
+ ClassI _ instances <- reify ''Flag
+ case dupes instances of
+ [] -> return ()
+ (dupe:_) -> fail ("Multiple definition of flag " ++ (snd $ head dupe) ++
+ ", modules: " ++ (show $ map fst dupe))
+ [| getArgs >>= initFlags progDescription $(listE $ map instanceToOptTuple instances ) |]
+ where
+ instanceToOptTuple (InstanceD _ (AppT _ inst) _) = [| getFlagData (undefined :: $(return inst)) |]
+ instanceToOptTuple _ = error "Shouldn't happen"
+ instanceToModuleNamePair (InstanceD _ (AppT _ (ConT inst)) _) =
+ let (flagrev, modrev) = span (/= '.') $ reverse $ show inst
+ modName = reverse $ drop 1 modrev
+ flag = drop 1 $ dropWhile (/= '_') $ reverse $ flagrev
+ in (modName, flag)
+ instanceToModuleNamePair _ = error "Shouldn't happen"
+ dupes instances = filter ((>1) . length) $
+ groupBy ((==) `on` snd) $
+ sortBy (compare `on` snd) $
+ map instanceToModuleNamePair instances
View
2  Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
View
72 examples/ComplexExample.hs
@@ -0,0 +1,72 @@
+#!/usr/bin/env runhaskell
+
+{-# LANGUAGE TemplateHaskell #-}
+
+import Control.Monad
+import System.Exit
+
+import HFlags
+
+-- For flags with a simple type (technically speaking, for instances
+-- of FlagType, see `:info FlagType' in GHCi), defining a new flag is
+-- very straightforward:
+defineFlag "name" "Indiana Jones" "Who to greet."
+-- There is a special syntax to support short options, like `d' here.
+-- Also, for the Bool options the argument is not mandatory, if the
+-- user just runs the program with -d or --dry_run, flags_dru_run will
+-- be set to True.
+defineFlag "d:dry_run" False "Don't print anything, just exit."
+-- For integral types you have to explicitly define Int or Integer.
+defineFlag "repeat" (3 + 4 :: Int) "Number of times to repeat the message."
+
+-- For flags with a more complex type, where the existing Read and
+-- Show is suitable for parsing of the argument value, you can use the
+-- defineQQFlag syntax. Here, the QQ is mnemonic for QuasiQuoter,
+-- because you have to quasiquote the default value, and type sign it
+-- inside the quasiquote. Also, you have to provide the name of the
+-- type for --help generation.
+defineQQFlag "numbers_to_sum" [| [1,2,3,4,5] :: [Int] |] "INT_LIST" "Print the sum of these numbers."
+
+-- This works quite well for simple enums too!
+data Color = Red | Yellow | Green deriving (Show, Read)
+defineQQFlag "favorite_color" [| Yellow :: Color |] "COLOR" "Your favorite color."
+
+-- Sometimes the default read or show instance is not good enough for
+-- your needs. In that case you can use defineCustomFlag to override
+-- those functions.
+data Language = English | Hungarian
+defineCustomFlag "language" [| English :: Language |] "en|hu"
+ [| \s -> case s of
+ "en" -> English
+ "hu" -> Hungarian
+ _ -> error $ "Unknown language: " ++ s
+ |]
+ [| \l -> case l of
+ English -> "en"
+ Hungarian -> "hu"
+ |]
+ "Language of the greeting."
+
+-- You can also do simple range checks with this.
+defineCustomFlag "percent" [| 100 :: Double |] "PERCENTAGE"
+ [| \s -> let p = read s
+ in if 0.0 <= p && p <= 100.0
+ then p
+ else error "Percentage value has to be between 0 and 100."
+ |]
+ [| show |]
+ "Print first percent percentage of the message."
+
+main = do
+ _ <- $(initHFlags "HFlags example program v0.1")
+ when (flags_dry_run) $ exitSuccess
+ forM_ [1..flags_repeat] (const greet)
+ putStrLn $ "IIRC, your favorite color is " ++ show flags_favorite_color ++ "."
+ where
+ s = show (sum flags_numbers_to_sum)
+ percentPutStrLn 0 _ = return ()
+ percentPutStrLn p str = let n = ceiling $ fromIntegral (length str) * p / 100.0
+ in putStrLn $ take n str
+ greet = percentPutStrLn flags_percent $ case flags_language of
+ English -> "Hello " ++ flags_name ++ ", very nice to meet you, the sum is " ++ s ++ "!"
+ Hungarian -> "Szia " ++ flags_name ++ ", orvendek a talalkozasnak, a szamok osszege " ++ s ++ "!"
View
9 examples/ImportExample.hs
@@ -0,0 +1,9 @@
+#!/usr/bin/env runhaskell
+
+{-# LANGUAGE TemplateHaskell #-}
+
+import HFlags
+import X.B
+
+main = do _ <- $(initHFlags "Importing example v0.1")
+ print $ b
View
13 examples/SimpleExample.hs
@@ -0,0 +1,13 @@
+#!/usr/bin/env runhaskell
+
+{-# LANGUAGE TemplateHaskell #-}
+
+import HFlags
+
+defineFlag "name" "Indiana Jones" "Who to greet."
+defineFlag "repeat" (3 + 4 :: Int) "Number of times to repeat the message."
+
+main = do s <- $(initHFlags "Simple program v0.1")
+ sequence_ $ replicate flags_repeat greet
+ where
+ greet = putStrLn $ "Hello " ++ flags_name ++ ", very nice to meet you!"
View
9 examples/X/B.hs
@@ -0,0 +1,9 @@
+module X.B (b) where
+
+import qualified X.Y_Y.A as A
+
+-- to test collision detection
+-- import HFlags
+-- defineFlag "verbose" True "Whether debug output should be printed."
+
+b = A.flags_verbose
View
7 examples/X/Y_Y/A.hs
@@ -0,0 +1,7 @@
+{-# LANGUAGE TemplateHaskell #-}
+
+module X.Y_Y.A where
+
+import HFlags
+
+defineFlag "verbose" True "Whether debug output should be printed."
View
76 hflags.cabal
@@ -0,0 +1,76 @@
+name: hflags
+version: 0.1
+license: OtherLicense
+license-file: COPYING
+author: Mihaly Barasz <klao@google.com>, Gergely Risko <errge@google.com>
+maintainer: Gergely Risko <errge@google.com>
+build-type: Simple
+cabal-version: >= 1.6
+category: Console
+stability: provisional
+homepage: http://github.com/errge/hflags
+bug-reports: mailto:errge@google.com
+
+synopsis: Command line flag parser, very similar to Google's gflags
+description:
+ The @HFlags@ library supports easy definition of command line flags,
+ reimplementing the ideas from Google's @gflags@
+ (<http://code.google.com/p/gflags>).
+ .
+ Command line flags can be declared in any file at the toplevel,
+ using 'defineFlag'. At runtime, the actual values are assigned to
+ the toplevel @flags_name@ constants. Those can be used purely
+ throughout the program.
+ .
+ At the beginning of the @main@ function, @$(initHFlags "program
+ description")@ has to be called to initialize the flags. All flags
+ will be initialized that are transitively reachable via imports from
+ @main@. This means, that any Haskell package can easily define
+ command line flags with @HFlags@. This feature is demonstrated by
+ <http://github.com/errge/hflags/blob/master/examples/ImportExample.hs>.
+ .
+ A simple example (more in the
+ <http://github.com/errge/hflags/tree/master/examples> directory):
+ .
+ @
+ \#!\/usr\/bin\/env runhaskell
+ .
+ &#x7b;-\# LANGUAGE TemplateHaskell \#-&#x7d;
+ .
+ import HFlags
+ .
+ 'defineFlag' \"name\" \"Indiana Jones\" \"Who to greet.\"
+ 'defineFlag' \"r:repeat\" (3 + 4 :: Int) \"Number of times to repeat the message.\"
+ .
+ main = do s <- $(initHFlags \"Simple program v0.1\")
+ &#x20; sequence_ $ replicate flags_repeat greet
+ &#x20; where
+ &#x20; greet = putStrLn $ \"Hello \" ++ flags_name ++ \", very nice to meet you!\"
+ @
+ .
+ At @initHFlags@ time, the library also tries to gather flags out of
+ environment variables. @HFLAGS_verbose=True@ is equivalent to
+ specify --verbose=True. This environment feature only works with
+ long options and the user has to specify a value even for Bools.
+
+extra-source-files:
+ examples/ComplexExample.hs
+ examples/ImportExample.hs
+ examples/SimpleExample.hs
+ examples/X/B.hs
+ examples/X/Y_Y/A.hs
+
+source-repository head
+ type: git
+ location: http://github.com/errge/hflags
+
+library
+ ghc-options: -Wall
+
+ build-depends:
+ base >= 4.5 && < 5
+ , containers >= 0.4
+ , template-haskell >= 2.7
+
+ exposed-modules:
+ HFlags
Please sign in to comment.
Something went wrong with that request. Please try again.