Data.ProtocolBuffers.Orphans

Messages containing Optional Enumeration fields fail to encode. This module contains orphan instances required to make these functional.

For more information reference the associated ticket: https://github.com/alphaHeavy/protobuf/issues/3

Documentation

class Foldable t

Data structures that can be folded.

Minimal complete definition: foldMap or foldr.

For example, given a data type

data Tree a = Empty | Leaf a | Node (Tree a) a (Tree a)

a suitable instance would be

instance Foldable Tree where
   foldMap f Empty = mempty
   foldMap f (Leaf x) = f x
   foldMap f (Node l k r) = foldMap f l `mappend` f k `mappend` foldMap f r

This is suitable even for abstract types, as the monoid is assumed to satisfy the monoid laws. Alternatively, one could define foldr:

instance Foldable Tree where
   foldr f z Empty = z
   foldr f z (Leaf x) = f x z
   foldr f z (Node l k r) = foldr f (f k (foldr f z r)) l

Minimal complete definition

foldMap | foldr

Instances

Foldable []

Foldable Last

Foldable Maybe

Foldable Fixed

Foldable Signed

Foldable PackedList

Foldable PackedField

Foldable Enumeration

Foldable Always

Foldable RepeatedField

Foldable OptionalField

Foldable RequiredField

Foldable Value

Foldable Message

Foldable (Either a)

Foldable ((,) a)

Ix i => Foldable (Array i)

Foldable (Const m)

Foldable (Proxy *)

Foldable (HashMap k)

Foldable (Field n)