[3.x] add popat! (#774)

Project.toml

@@ -1,6 +1,6 @@
 name = "Compat"
 uuid = "34da2185-b29b-5c13-b0c7-acf172513d20"
-version = "3.44.0"
+version = "3.45.0"
 
 [deps]
 Base64 = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"

README.md

@@ -69,6 +69,9 @@ changes in `julia`.
 
 ## Supported features
 
+* `popat!` removes the item at the given `i` and returns it ([#36070]). (since
+  Compat 3.45.0)
+
 * `keepat!` removes the items at all the indices which are not given and returns
   the modified source ([#36229], [#42351]). (since Compat 3.44.0, 4.1.0)
 
@@ -298,6 +301,7 @@ Note that you should specify the correct minimum version for `Compat` in the
 [#29790]: https://github.com/JuliaLang/julia/pull/29790
 [#38449]: https://github.com/JuliaLang/julia/pull/38449
 [#36018]: https://github.com/JuliaLang/julia/pull/36018
+[#36070]: https://github.com/JuliaLang/julia/pull/36070
 [#36199]: https://github.com/JuliaLang/julia/pull/36199
 [#37454]: https://github.com/JuliaLang/julia/pull/37454
 [#40729]: https://github.com/JuliaLang/julia/pull/40729

src/Compat.jl

@@ -1365,6 +1365,27 @@ end
     end
 end
 
+# This function is available as of Julia 1.5.
+@static if !isdefined(Base, :popat!)
+    export popat!
+
+    function popat!(a::Vector, i::Integer)
+        x = a[i]
+        Base._deleteat!(a, i, 1)
+        x
+    end
+
+    function popat!(a::Vector, i::Integer, default)
+        if 1 <= i <= length(a)
+            x = @inbounds a[i]
+            Base._deleteat!(a, i, 1)
+            x
+        else
+            default
+        end
+    end
+end
+
 include("iterators.jl")
 include("deprecated.jl")
 

test/runtests.jl

@@ -1451,3 +1451,18 @@ end
     keepat!(ea, Bool[])
     @test isempty(ea)
 end
+
+@testset "popat!(::Vector, i, [default])" begin
+    a = [1, 2, 3, 4]
+    @test_throws BoundsError popat!(a, 0)
+    @test popat!(a, 0, "default") == "default"
+    @test a == 1:4
+    @test_throws BoundsError popat!(a, 5)
+    @test popat!(a, 1) == 1
+    @test a == [2, 3, 4]
+    @test popat!(a, 2) == 3
+    @test a == [2, 4]
+    @test popat!(a, 1, "default") == 2
+    badpop() = @inbounds popat!([1], 2)
+    @test_throws BoundsError badpop()
+end