base64-lens: Optics for the Base64 library

This is a package candidate release! Here you can preview how this package release will appear once published to the main package index (which can be accomplished via the 'maintain' link below). Please note that once a package has been published to the main package index it cannot be undone! Please consult the package uploading documentation for more information.

[maintain] [Publish]

Prisms and pattern synonyms for the Base64 library


[Skip to Readme]

Properties

Versions 0.1.0.0, 0.1.0.1, 0.1.0.1, 0.1.0.3, 0.2.0, 0.3.0, 0.3.1
Change log CHANGELOG.md
Dependencies base (>=4.10 && <5), base64 (>=0.2 && <0.3), bytestring (>=0.10 && <0.11), lens (>=4.0 && <4.19), text (>=1.2 && <1.3) [details]
License BSD-3-Clause
Copyright (c) 2019 Emily Pillmore
Author Emily Pillmore
Maintainer emilypi@cohomolo.gy
Category Data
Home page https://github.com/emilypi/base64-lens
Bug tracker https://github.com/emilypi/base64-lens/issues
Source repo head: git clone https://github.com/emilypi/base64.git
Uploaded by topos at 2020-01-07T05:52:46Z

Modules

[Index] [Quick Jump]

Downloads

Maintainer's Corner

Package maintainers

For package maintainers and hackage trustees


Readme for base64-lens-0.1.0.1

[back to package description]

Base64-lens

Build Status Hackage

This package provides optics and convenient pattern synonyms for the base64 library.

Patterns

The pattern synonyms provided in this library are:

pattern Base64 :: ByteString -> ByteString
pattern Base64Url :: ByteString -> ByteString
pattern Base64Unpadded :: ByteString -> ByteString
pattern Base64UrlUnpadded :: ByteString -> ByteString

-- and

pattern Base64 :: Text -> Text
pattern Base64Url :: Text -> Text
pattern Base64Unpadded :: Text -> Text
pattern Base64UrlUnpadded :: Text -> Text

These provide a convenient high level interface for passing Base64 encoded values.

Optics

Prisms for encoding and decoding Text and ByteString values are given as part of the library:

_Base64 :: Prism' ByteString ByteString
_Base64Url :: Prism' ByteString ByteString
_Base64Unpadded :: Prism' ByteString ByteString
_Base64UrlUnpadded :: Prism' ByteString ByteString

-- and

_Base64 :: Prism' Text Text
_Base64Url :: Prism' Text Text
_Base64Unpadded :: Prism' Text Text
_Base64UrlUnpadded :: Prism' Text Text

If a particular structure has a Lens into some Text or ByteString value they might want to encode (or decode), then composing such a Lens with these Prisms yields an affine Traversal, resulting in a structure which has the focus of its Lens encoded as or decoded from Base64(-url). All one needs to do is compose their optics:


data MyStruct = MyStruct
  { _a :: Int
  , _b :: Text
  } deriving Show

b :: Lens' MyStruct Text
b = lens _b (\t b_ -> t { _b = b_ })

myB64Struct :: Traversal' s Text
myB64Struct = b . _Base64

-- >>> MyStruct 3 "U3Vu" ^? b . _Base64
-- MyStruct {_a = 3, _b = "Sun"}

bRe :: Review MyStruct Text
bRe = unto (\b -> MyStruct 0 b)

-- >>> bRe . _Base64 # "Sun"
-- MyStruct {_a = 0, _b = "UV3u"}

The data of a Prism naturally conforms to this "encoding/decoding" dichotomy, where the Review, or "builder" half of the Prism of type b -> t is an encoding, and the "Matcher" half of the prism, of type s -> Either t a, represents a decoding of a similar structure. Hence, Prism is the most appropriate structure.