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Update typeclasses.md
tsobako Oct 27, 2022
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Update typeclasses.md
tsobako Oct 27, 2022
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Update inforgraphic for new cats version
tsobako Nov 3, 2022
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Remove svg typeclass graph and add mermaid version
tsobako Nov 7, 2022
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Fix tabs in mermaid graph
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Refactor typeclass mermaid diagram
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262 changes: 260 additions & 2 deletions docs/typeclasses.md
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Original file line number Diff line number Diff line change
@@ -1,4 +1,8 @@
# Type Classes

<script src="https://cdn.jsdelivr.net/npm/mermaid/dist/mermaid.min.js"></script>
<script>mermaid.initialize({startOnLoad:true});</script>

Type classes are a powerful tool used in functional programming to enable ad-hoc polymorphism, more commonly
known as overloading. Where many object-oriented languages leverage subtyping for polymorphic code, functional
programming tends towards a combination of parametric polymorphism (think type parameters, like Java generics)
Expand Down Expand Up @@ -227,8 +231,262 @@ You can find out more about law testing [here](typeclasses/lawtesting.md).

## Type classes in Cats

<img src="https://cdn.rawgit.com/tpolecat/cats-infographic/master/cats.svg" alt="infographic" style="width: 100%;"/>
From [cats-infographic by @tpolecat](https://github.com/tpolecat/cats-infographic).
Dotted line means that typeclass does not inherit other typeclass, but uses it.
The highlighted type classes are the most important to learn in particular library.

```mermaid
graph BT;
classDef kernel fill:#FF99FF,stroke-width:2px,stroke:#000;
classDef kernelImportant fill:#FF00FF,stroke-width:2px,stroke:#000;

subgraph kernel
direction BT
id1(Eq):::kernelImportant;
id2(PartialOrder):::kernel;
id3(Hash):::kernel;
id4(Order):::kernelImportant;

id2-->id1;
id3-->id1;
id4-->id2;
end

subgraph kernel
direction BT
id8(Semigroup):::kernelImportant;
id9(Band):::kernel;
id10(CommutativeSemigroup):::kernel;
id11(Monoid):::kernelImportant;
id12(Semilattice):::kernel;
id13(CommutativeMonoid):::kernel;
id14(Group):::kernel;
id15(BoundedSemilattice):::kernel;
id16(CommutativeGroup):::kernel;

id9-->id8;
id10-->id8;
id11-->id8;
id12-->id9;
id12-->id10;
id13-->id10;
id13-->id11;
id14-->id11;
id15-->id12;
id15-->id13;
id16-->id13;
id16-->id14;
end
```

```mermaid
graph BT;
classDef core fill:#BBBBFF,stroke-width:2px,stroke:#000;

subgraph core
direction BT
id5(Bifoldable):::core;
id6(Bifunctor):::core;
id7(Bitraverse):::core;
id79(NotNull):::core;
id80(Show):::core;
id81(Inject):::core;
id82(InjectK):::core;
id83(Parallel):::core;
id84(NonEmptyParallel):::core;

id7-->id5;
id7-->id6;
id83-->id84;
end
```

```mermaid
graph BT;

classDef core fill:#BBBBFF,stroke-width:2px,stroke:#000;
classDef coreImportant fill:#6666FF,stroke-width:2px,stroke:#000;

subgraph core
direction BT
id25(UnorderedFoldable):::core;
id26(UnorderedTraverse):::core;
id27(Invariant):::core;
id28(Foldable):::coreImportant;
id29(Functor):::coreImportant;
id30(Semigroupal):::core;
id31(Contravariant):::core;
id32(Reducible):::core;
id33(Traverse):::coreImportant;
id34(InvariantSemigroupal):::core;
id35(ContravariantSemigroupal):::core;
id36(NonEmptyTraverse):::core;
id37(Distributive):::core;
id38(Apply):::core;
id39(InvariantMonoidal):::core;
id40(CoflatMap):::core;
id41(FlatMap):::core;
id42(CommutativeApply):::core;
id43(Applicative):::coreImportant;
id44(ContravariantMonoidal):::core;
id45(Comonad):::core;
id46(CommutativeFlatMap):::core;
id47(Monad):::coreImportant;
id48(CommutativeApplicative):::core;
id49(ApplicativeError):::core;
id50(Bimonad):::core;
id51(CommutativeMonad):::core;
id52(MonadError):::core;
id53(SemigroupK):::core;
id56(NonEmptyAlternative):::core;
id54(MonoidK):::core;
id55(Alternative):::coreImportant;

id26-->id25;
id28-->id25;
id29-->id27;
id31-->id27;
id32-->id28;
id33-->id26;
id33-->id28;
id33-->id29;
id34-->id27;
id34-->id30;
id35-->id31;
id35-->id34;
id36-->id32;
id36-->id33;
id38-->id29;
id38-->id34;
id39-->id34;
id40-->id29;
id37-->id29;
id41-->id38;
id42-->id38;
id43-->id38;
id43-->id39;
id44-->id35;
id44-->id39;
id45-->id40;
id46-->id41;
id46-->id42;
id47-->id41;
id47-->id43;
id48-->id42;
id48-->id43;
id49-->id43;
id50-->id45;
id50-->id47;
id51-->id46;
id51-->id47;
id51-->id48;
id52-->id47;
id52-->id49;
id56-->id43;
id56-->id53;
id55-->id43;
id55-->id54;
id55-->id56;
id54-->id53;
end
```

```mermaid
graph BT;
classDef core fill:#BBBBFF,stroke-width:2px,stroke:#000;
classDef effect fill:#FFFF00,stroke-width:2px,stroke:#000;

subgraph effect
direction BT
id52(MonadError):::core;
id57(Unique):::effect;
id58(MonadCancel):::effect;
id59(GenSpawn):::effect;
id60(Clock):::effect;
id61(GenConcurrent):::effect;
id62(Defer):::effect;
id63(GenTemporal):::effect;
id64(Sync):::effect;
id65(Async):::effect;

id58-->id52;
id59-->id57;
id59-->id58;
id61-->id59;
id63-->id60;
id63-->id61;
id64-->id57;
id64-->id58;
id64-->id60;
id64-->id62;
id65-->id63;
id65-->id64;
end
```

```mermaid
graph BT;
classDef arrow fill:#FFFF99,stroke-width:2px,stroke:#000;

subgraph arrow
direction BT
id17(Compose):::arrow;
id18(Profunctor):::arrow;
id19(Category):::arrow;
id20(Strong):::arrow;
id21(Choice):::arrow;
id22(Arrow):::arrow;
id23(ArrowChoice):::arrow;
id24(CommutaticeArrow):::arrow;

id19-->id17;
id20-->id18;
id21-->id19;
id22-->id19;
id22-->id20;
id23-->id21;
id23-->id22;
id24-->id22;
end
```

```mermaid
graph BT;

classDef coreInMtl fill:#AAAA88,stroke-width:2px,stroke:#000;
classDef mtl fill:#FFBBBB,stroke-width:2px,stroke:#000;

subgraph mtl
direction BT
id66(Applicative):::coreInMtl;
id67(Functor):::coreInMtl;
id68(Ask):::mtl;
id69(Raise):::mtl;
id70(Tell):::mtl;
id71(Local):::mtl;
id72(Handle):::mtl;
id73(Listen):::mtl;
id74(Monoid):::coreInMtl;
id75(Monad):::coreInMtl;
id76(Censor):::mtl;
id77(Stateful):::mtl;
id78(Chronicle):::mtl;

id68-.->id66;
id69-.->id67;
id70-.->id67;
id71--->id68;
id72-.->id66;
id72--->id69;
id73--->id70;
id76--->id73;
id76-.->id74;
id77-.->id75;
id78-.->id75;
id76-.->id66;
end
```

(The typeclass graph based on @tpolecat's repository `cats-infographic`).


## Incomplete type class instances in cats
Expand Down