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‎README.md

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# CircularArrayBuffers
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[![Build Status](https://github.com/JuliaReinforcementLearning/CircularArrayBuffers.jl/workflows/CI/badge.svg)](https://github.com/JuliaReinforcementLearning/CircularArrayBuffers.jl/actions)
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`CircularArrayBuffers.jl` is a small package to wrap an `AbstractArray` as a buffer along the last dimension. The main benefit compared to [`CircularBuffer`](https://juliacollections.github.io/DataStructures.jl/latest/circ_buffer/) in [`DataStructures.jl`](https://github.com/JuliaCollections/DataStructures.jl) is that the view of consecutive elements is a `SubArray`.
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## Usage
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```julia
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julia> using CircularArrayBuffers
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julia> names(CircularArrayBuffers)
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5-element Array{Symbol,1}:
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:CircularArrayBuffer
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:CircularArrayBuffers
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:CircularVectorBuffer
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:capacity
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:isfull
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julia> a = CircularArrayBuffer(rand(2,3))
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2×3 CircularArrayBuffer{Float64,2}:
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0.0510714 0.0260738 0.0245707
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0.856257 0.571643 0.0189365
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julia> b = CircularArrayBuffer{Float64}(2,3)
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2×0 CircularArrayBuffer{Float64,2}
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julia> push!(b, rand(2))
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2×1 CircularArrayBuffer{Float64,2}:
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0.4215856115651755
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0.5485806794787502
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julia> push!(b, rand(2))
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2×2 CircularArrayBuffer{Float64,2}:
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0.421586 0.640501
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0.548581 0.774729
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julia> push!(b, rand(2))
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2×3 CircularArrayBuffer{Float64,2}:
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0.421586 0.640501 0.653054
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0.548581 0.774729 0.902611
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julia> push!(b, rand(2))
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2×3 CircularArrayBuffer{Float64,2}:
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0.640501 0.653054 0.640373
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0.774729 0.902611 0.227435
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julia> pop!(b)
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2-element view(::CircularArrayBuffer{Float64,2}, :, 3) with eltype Float64:
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0.6403725468830439
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0.22743495787074597
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julia> b
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2×2 CircularArrayBuffer{Float64,2}:
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0.640501 0.653054
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0.774729 0.902611
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julia> size(b)
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(2, 2)
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julia> capacity(b)
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3
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julia> isfull(b)
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false
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julia> push!(b, rand(2))
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2×3 CircularArrayBuffer{Float64,2}:
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0.640501 0.653054 0.885887
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0.774729 0.902611 0.0332439
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julia> isfull(b)
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true
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julia> eltype(b)
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Float64
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```

‎src/CircularArrayBuffers.jl

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module CircularArrayBuffers
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# Write your package code here.
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export CircularArrayBuffer, CircularVectorBuffer, capacity, isfull
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"""
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CircularArrayBuffer{T}(sz::Integer...) -> CircularArrayBuffer{T, N}
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`CircularArrayBuffer` uses a `N`-dimension `Array` of size `sz` to serve as a buffer for
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`N-1`-dimension `Array`s of the same size.
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"""
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mutable struct CircularArrayBuffer{T,N} <: AbstractArray{T,N}
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buffer::Array{T,N}
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first::Int
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nframes::Int
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step_size::Int
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end
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const CircularVectorBuffer{T} = CircularArrayBuffer{T, 1}
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function CircularArrayBuffer{T}(d::Integer...) where {T}
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N = length(d)
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CircularArrayBuffer(Array{T}(undef, d...), 1, 0, N == 1 ? 1 : *(d[1:end-1]...))
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end
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function CircularArrayBuffer(A::AbstractArray{T,N}) where {T,N}
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CircularArrayBuffer(A, 1, size(A, N), N == 1 ? 1 : *(size(A)[1:end-1]...))
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end
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Base.IndexStyle(::CircularArrayBuffer) = IndexLinear()
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Base.size(cb::CircularArrayBuffer{T,N}, i::Integer) where {T,N} = i == N ? cb.nframes : size(cb.buffer, i)
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Base.size(cb::CircularArrayBuffer{T,N}) where {T,N} = ntuple(i -> size(cb, i), N)
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Base.getindex(cb::CircularArrayBuffer{T,N}, i::Int) where {T,N} = getindex(cb.buffer, _buffer_index(cb, i))
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Base.setindex!(cb::CircularArrayBuffer{T,N}, v, i::Int) where {T,N} = setindex!(cb.buffer, v, _buffer_index(cb, i))
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capacity(cb::CircularArrayBuffer{T,N}) where {T,N} = size(cb.buffer, N)
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isfull(cb::CircularArrayBuffer) = cb.nframes == capacity(cb)
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Base.isempty(cb::CircularArrayBuffer) = cb.nframes == 0
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@inline function _buffer_index(cb::CircularArrayBuffer, i::Int)
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ind = (cb.first - 1) * cb.step_size + i
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mod1(ind, length(cb.buffer))
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end
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@inline function _buffer_frame(cb::CircularArrayBuffer, i::Int)
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n = capacity(cb)
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idx = cb.first + i - 1
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mod1(idx, n)
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end
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_buffer_frame(cb::CircularArrayBuffer, I::Vector{Int}) = map(i -> _buffer_frame(cb, i), I)
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function Base.empty!(cb::CircularArrayBuffer)
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cb.nframes = 0
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cb
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end
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function Base.push!(cb::CircularArrayBuffer{T, N}, data) where {T,N}
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if cb.nframes == capacity(cb)
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cb.first = (cb.first == capacity(cb) ? 1 : cb.first + 1)
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else
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cb.nframes += 1
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end
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if N == 1
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cb[cb.nframes] = data
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else
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cb[ntuple(_ -> (:), N - 1)..., cb.nframes] .= data
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end
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cb
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end
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function Base.pop!(cb::CircularArrayBuffer{T, N}) where {T,N}
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if cb.nframes <= 0
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throw(ArgumentError("buffer must be non-empty"))
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else
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res = @views cb[ntuple(_ -> (:), N - 1)..., cb.nframes]
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cb.nframes -= 1
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res
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end
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end
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end

‎test/runtests.jl

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using Test
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@testset "CircularArrayBuffers.jl" begin
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# Write your tests here.
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A = ones(2, 2)
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C = ones(Float32, 2, 2)
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@testset "1D Int" begin
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b = CircularArrayBuffer{Int}(3)
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@test eltype(b) == Int
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@test capacity(b) == 3
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@test isfull(b) == false
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@test isempty(b) == true
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@test length(b) == 0
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@test size(b) == (0,)
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# element must has the exact same length with the element of buffer
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@test_throws Exception push!(b, [1, 2])
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for x in 1:3
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push!(b, x)
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end
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@test capacity(b) == 3
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@test isfull(b) == true
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@test length(b) == 3
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@test size(b) == (3,)
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@test b[1] == 1
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@test b[end] == 3
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@test b[1:end] == [1, 2, 3]
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for x in 4:5
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push!(b, x)
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end
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@test capacity(b) == 3
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@test length(b) == 3
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@test size(b) == (3,)
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@test b[1] == 3
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@test b[end] == 5
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@test b[1:end] == [3, 4, 5]
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empty!(b)
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@test isfull(b) == false
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@test isempty(b) == true
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@test length(b) == 0
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@test size(b) == (0,)
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push!(b, 6)
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@test isfull(b) == false
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@test isempty(b) == false
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@test length(b) == 1
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@test size(b) == (1,)
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@test b[1] == 6
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push!(b, 7)
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push!(b, 8)
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@test isfull(b) == true
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@test isempty(b) == false
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@test length(b) == 3
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@test size(b) == (3,)
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@test b[[1, 2, 3]] == [6, 7, 8]
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push!(b, 9)
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@test isfull(b) == true
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@test isempty(b) == false
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@test length(b) == 3
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@test size(b) == (3,)
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@test b[[1, 2, 3]] == [7, 8, 9]
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x = pop!(b)
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@test x == 9
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@test length(b) == 2
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@test b[[1, 2]] == [7, 8]
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x = pop!(b)
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@test x == 8
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@test length(b) == 1
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@test b[1] == 7
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x = pop!(b)
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@test x == 7
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@test length(b) == 0
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@test_throws ArgumentError pop!(b)
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end
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@testset "2D Float64" begin
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b = CircularArrayBuffer{Float64}(2, 2, 3)
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@test eltype(b) == Float64
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@test capacity(b) == 3
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@test isfull(b) == false
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@test length(b) == 0
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@test size(b) == (2, 2, 0)
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for x in 1:3
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push!(b, x * A)
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end
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@test capacity(b) == 3
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@test isfull(b) == true
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@test length(b) == 2 * 2 * 3
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@test size(b) == (2, 2, 3)
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for i in 1:3
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@test b[:, :, i] == i * A
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end
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@test b[:, :, end] == 3 * A
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for x in 4:5
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push!(b, x * ones(2, 2))
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end
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@test capacity(b) == 3
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@test length(b) == 2 * 2 * 3
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@test size(b) == (2, 2, 3)
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@test b[:, :, 1] == 3 * A
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@test b[:, :, end] == 5 * A
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@test b == reshape([c for x in 3:5 for c in x * A], 2, 2, 3)
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push!(b, 6 * ones(Float32, 2, 2))
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push!(b, 7 * ones(Int, 2, 2))
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@test b == reshape([c for x in 5:7 for c in x * A], 2, 2, 3)
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x = pop!(b)
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@test x == 7 * ones(2,2)
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@test b == reshape([c for x in 5:6 for c in x * A], 2, 2, 2)
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end
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end

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