merge: A functor for consistent merging of information

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A functor for consistent merging of information.


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Versions [RSS] 0.1.0.0, 0.2.0.0, 0.3.0.0, 0.3.0.1, 0.3.1.1
Change log CHANGELOG.md
Dependencies base (>=4.6 && <5), profunctors (>=5.6 && <6) [details]
License MIT
Copyright 2020 Samuel Schlesinger
Author Samuel Schlesinger
Maintainer sgschlesinger@gmail.com
Category Data
Source repo head: git clone https://github.com/samuelschlesinger/merge
Uploaded by sgschlesinger at 2021-09-18T02:30:25Z
Distributions NixOS:0.3.1.1
Downloads 446 total (1 in the last 30 days)
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Status Docs available [build log]
Last success reported on 2021-09-18 [all 1 reports]

Readme for merge-0.3.0.0

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Merge

Often, one finds themselves having multiple sources of knowledge for some piece of data, and having to merge these together. Perhaps we have a type representing partial information about a digital friend.

data Friend = Friend
  { name :: Maybe Text
  , email :: Maybe Text
  , age :: Int
  , pubKey :: PublicKey
  }

If we learn some information about a friend from someone, and some from someone else, we'll want to merge that information to have a more complete picture. That said, it might not succeed, as we may have inconsistent information like two different names or different public keys. We'll want a function of type:

f :: Friend -> Friend -> Maybe Friend

That's the pattern that this library encapsulates!

mergeFriends :: Merge Friend Friend
mergeFriends =
  User
    <$> optional name
    <*> optional email
    <*> combine Max
    <*> required pubKey

f :: Friend -> Friend -> Maybe Friend
f x y = runMerge mergeFriends x y