add pop!(vector, idx, [default]) (#35513)

NEWS.md

@@ -122,6 +122,7 @@ New library features
 * `x::Signed % Unsigned` and `x::Unsigned % Signed` are supported for integer bitstypes.
 * `signed(unsigned_type)` is supported for integer bitstypes, `unsigned(signed_type)` has been supported.
 * `accumulate`, `cumsum`, and `cumprod` now support `Tuple` ([#34654]) and arbitrary iterators ([#34656]).
+* `pop!(collection, key, [default])` now has a method for `Vector` to remove an element at an arbitrary index ([#35513]).
 * In `splice!` with no replacement, values to be removed can now be specified with an
   arbitrary iterable (instead of a `UnitRange`) ([#34524]).
 * The `@view` and `@views` macros now support the `a[begin]` syntax that was introduced in Julia 1.4 ([#35289]).

base/array.jl

@@ -1129,6 +1129,22 @@ function pop!(a::Vector)
     return item
 end
 
+function pop!(a::Vector, i::Integer)
+    x = a[i]
+    _deleteat!(a, i, 1)
+    x
+end
+
+function pop!(a::Vector, i::Integer, default)
+    if 1 <= i <= length(a)
+        x = @inbounds a[i]
+        _deleteat!(a, i, 1)
+        x
+    else
+        default
+    end
+end
+
 """
     pushfirst!(collection, items...) -> collection
 

base/dict.jl

@@ -576,6 +576,9 @@ end
 Delete and return the mapping for `key` if it exists in `collection`, otherwise return
 `default`, or throw an error if `default` is not specified.
 
+!!! compat "Julia 1.5"
+    For `collection::Vector`, this method requires at least Julia 1.5.
+
 # Examples
 ```jldoctest
 julia> d = Dict("a"=>1, "b"=>2, "c"=>3);

test/arrayops.jl

@@ -466,6 +466,21 @@ end
     end
     @test_throws BoundsError insert!(v, 5, 5)
 end
+
+@testset "pop!(::Vector, i, [default])" begin
+    a = [1, 2, 3, 4]
+    @test_throws BoundsError pop!(a, 0)
+    @test pop!(a, 0, "default") == "default"
+    @test a == 1:4
+    @test_throws BoundsError pop!(a, 5)
+    @test pop!(a, 1) == 1
+    @test a == [2, 3, 4]
+    @test pop!(a, 2) == 3
+    @test a == [2, 4]
+    badpop() = @inbounds pop!([1], 2)
+    @test_throws BoundsError badpop()
+end
+
 @testset "concatenation" begin
     @test isequal([fill(1.,2,2)  fill(2.,2,1)], [1. 1 2; 1 1 2])
     @test isequal([fill(1.,2,2); fill(2.,1,2)], [1. 1; 1 1; 2 2])