Merge #1654

1654: add Functors docs r=DhairyaLGandhi a=DhairyaLGandhi

Close #1653 

Co-authored-by: Dhairya Gandhi <dhairya@juliacomputing.com>

Author: bors[bot]

docs/Project.toml

@@ -1,5 +1,6 @@
 [deps]
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
+Functors = "d9f16b24-f501-4c13-a1f2-28368ffc5196"
 NNlib = "872c559c-99b0-510c-b3b7-b6c96a88d5cd"
 
 [compat]

docs/make.jl

@@ -1,7 +1,7 @@
-using Documenter, Flux, NNlib
+using Documenter, Flux, NNlib, Functors
 
-DocMeta.setdocmeta!(Flux, :DocTestSetup, :(using Flux); recursive=true)
-makedocs(modules=[Flux, NNlib],
+DocMeta.setdocmeta!(Flux, :DocTestSetup, :(using Flux); recursive = true)
+makedocs(modules = [Flux, NNlib, Functors],
          doctest = VERSION == v"1.5",
          sitename = "Flux",
          pages = ["Home" => "index.md",
@@ -13,7 +13,8 @@ makedocs(modules=[Flux, NNlib],
                      "Loss Functions" => "models/losses.md",
                      "Regularisation" => "models/regularisation.md",
                      "Advanced Model Building" => "models/advanced.md",
-                     "NNlib" => "models/nnlib.md"],
+                     "NNlib" => "models/nnlib.md",
+                     "Functors" => "models/functors.md"],
                   "Handling Data" =>
                     ["One-Hot Encoding" => "data/onehot.md",
                      "DataLoader" => "data/dataloader.md"],

docs/src/models/functors.md

@@ -0,0 +1,13 @@
+## Functors.jl
+
+Flux makes use of the Functors.jl to represent many of the core functionalities it provides.
+
+Functors.jl is a collection of tools designed to represent a [functor](https://en.wikipedia.org/wiki/Functor_(functional_programming)). Flux makes use of it to treat certain structs as functors. Notable examples include the layers that Flux defines.
+
+```@docs
+Functors.isleaf
+Functors.children
+Functors.fcollect
+Functors.functor
+Functors.fmap
+```