This is a packet that provides a very easy way to create command line argument parsers using convention over configuration. It does not intend to replace packages like cmdargs but it's scope is quick prototyping of applications. If you are, for example, in the early development of an application, Kwargs allows you to easily create a command line argument parser which you can later replace with something more powerful like cmdargs. With all honesty, I wrote this to improve the quality of homework assignments w/o having to do much.
- Define your settings type, which derives from generic. Make sure the 'DeriveGeneric' compiler flag is turned on:
{-# Language DeriveGeneric -#}
import GHC.Generics
data Config = Config{
o1 :: String, -- Regular string specified by --o1=value
o2 :: Bool, -- Flag which is set to True when --o2 is passed and set to False when not passed
o3 :: Maybe String, -- Same as option1 but it is set to Nothing when --o3 is not present
o4a_o4b :: Maybe (String, String) -- It is set to Nothing when neither flag is present,
-- set to the value 'Just (val1,val2) when --o4a=val1 and --o4b=val2 is present
-- Fails if only one of the two flags is present
} deriving (Generic, Show)
- Read the argumetns:
import System.Console.CmdArgs.Generic (kwargs, getBuilders)
import Control.Applicative ((<$>)) -- For syntactic convenience
main = (kwargs (getBuilders :: BaseBuilder Config) <$> getArgs) >>= print
- Assuming that the code from step 2 is compiled into an executable called 'args':
> args --o1=v1 --o2 --o3=v2 --o4a=v3 --o4b=v4
Right (Config{o1="v1", o2=True, o3=Just "v3", o4=Just ("v3","v4")})
> args --o1=v1 --o4a=v3 --o4b=v4
Right (Config{o1="v1", o2=False, o3=Nothing, o4=Just ("v3","v4")})
> args --o2 --o3=v2 --o4a=v3 --o4b=v4
Left ("--o1 is missing")
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent