salak-0.1.9: README.md

# salak

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Configuration Loader for Production in Haskell.

This library default a standard configuration load process. It can load properties from `CommandLine`, `Environment`,
`JSON value` and `Yaml` files. They all load to the same format `SourcePack`. Earler property source has higher order
to load property. For example:

```
CommandLine:  --package.a.enabled=true
Environment: PACKAGE_A_ENABLED: false

lookup "package.a.enabled" properties => Just True
```

`CommandLine` has higher order then `Environment`, for the former load properties earler then later.

Usage:

```Haskell
data Config = Config
  { name :: Text
  , dir  :: Maybe Text
  , ext  :: Int
  } deriving (Eq, Show)

instance FromProp Config where
  fromProp = Config
    <$> "user"
    <*> "pwd"
    <*> "ext" .?= 1

main = do
  c :: Config <- defaultLoadSalak def $ require ""
  print c
```

```
λ> c
Config {name = "daniel", dir = Nothing, ext = 1}
```