From ee09e5d0656603d51a6215433fad9c20d2d57e64 Mon Sep 17 00:00:00 2001
From: Takafumi Arakaki <aka.tkf@gmail.com>
Date: Tue, 15 Oct 2019 22:32:02 -0700
Subject: [PATCH] Function composition for multiple functions
 (JuliaLang/julia#33568)

---
 README.md        | 4 ++++
 src/Compat.jl    | 5 +++++
 test/runtests.jl | 7 +++++++
 3 files changed, 16 insertions(+)

diff --git a/README.md b/README.md
index 0b1a801d4..113cee93e 100644
--- a/README.md
+++ b/README.md
@@ -69,6 +69,9 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 ## Other changes
 
+* Function composition now supports multiple functions: `∘(f, g, h) = f ∘ g ∘ h`
+  and splatting `∘(fs...)` for composing an iterable collection of functions ([#33568]).
+
 ## New types
 
 ## Developer tips
@@ -127,3 +130,4 @@ includes this fix. Find the minimum version from there.
 [#29749]: https://github.com/JuliaLang/julia/issues/29749
 [#32628]: https://github.com/JuliaLang/julia/issues/32628
 [#33129]: https://github.com/JuliaLang/julia/issues/33129
+[#33568]: https://github.com/JuliaLang/julia/pull/33568
diff --git a/src/Compat.jl b/src/Compat.jl
index e9d2d2fb6..e4946a6d2 100644
--- a/src/Compat.jl
+++ b/src/Compat.jl
@@ -88,6 +88,11 @@ if VERSION < v"1.3.0-alpha.8"
     Base.mod(i::Integer, r::AbstractUnitRange{<:Integer}) = mod(i-first(r), length(r)) + first(r)
 end
 
+# https://github.com/JuliaLang/julia/pull/33568
+if VERSION < v"1.4.0-DEV.329"
+    Base.:∘(f, g, h...) = ∘(f ∘ g, h...)
+end
+
 include("deprecated.jl")
 
 end # module Compat
diff --git a/test/runtests.jl b/test/runtests.jl
index af6b808ee..6e1f8b77c 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -90,4 +90,11 @@ end
     @test_throws DivideError mod(3, 1:0)
 end
 
+# https://github.com/JuliaLang/julia/pull/33568
+@testset "function composition" begin
+    @test ∘(x -> x-2, x -> x-3, x -> x+5)(7) == 7
+    fs = [x -> x[1:2], uppercase, lowercase]
+    @test ∘(fs...)("ABC") == "AB"
+end
+
 nothing