Iterators.cycle(iter, n) (#819)

README.md

@@ -70,6 +70,8 @@ changes in `julia`.
 
 ## Supported features
 
+* `Iterators.cycle(itr, n)` is the lazy version of `repeat(vector, n)`. ([#47354]) (since Compat 4.13.0)
+
 * `@compat public foo, bar` marks `foo` and `bar` as public in Julia 1.11+ and is a no-op in Julia 1.10 and earlier. ([#50105]) (since Compat 3.47.0, 4.10.0)
 
 * `redirect_stdio`, for simple stream redirection. ([#37978]) (since Compat 4.8.0)

src/Compat.jl

@@ -775,6 +775,11 @@ if VERSION < v"1.9.0-DEV.461"
     Base.VersionNumber(v::VersionNumber) = v
 end
 
+# https://github.com/JuliaLang/julia/pull/47354
+if VERSION < v"1.11.0-DEV.1579"
+    Iterators.cycle(xs, n::Integer) = Iterators.flatten(Iterators.repeated(xs, n))
+end
+
 include("deprecated.jl")
 
 end # module Compat

test/runtests.jl

@@ -734,3 +734,21 @@ end
     v = VersionNumber("1.2.3")
     @test VersionNumber(v) === v
 end
+
+# https://github.com/JuliaLang/julia/pull/47354
+@testset "cycle(iter, n)"  begin
+    using Base.Iterators: cycle
+    @test collect(cycle(0:3, 2)) == [0, 1, 2, 3, 0, 1, 2, 3]
+    @test collect(cycle(Iterators.filter(iseven, 1:4), 2)) == [2, 4, 2, 4]
+    # @test collect(take(cycle(countfrom(11), 3), 4)) == 11:14  # this iterator is defined in Base's tests
+
+    @test isempty(cycle(1:0)) == isempty(cycle(1:0, 3)) == true
+    @test isempty(cycle(1:5, 0))
+    @test isempty(cycle(Iterators.filter(iseven, 1:4), 0))
+
+    @test eltype(cycle(0:3, 2)) === Int
+    @test Base.IteratorEltype(cycle(0:3, 2)) == Base.HasEltype()
+
+    Base.haslength(cycle(0:3, 2)) == false  # but not sure we should test these
+    Base.IteratorSize(cycle(0:3, 2)) == Base.SizeUnknown()
+end