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Jun 10, 2025
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Random: make randperm! and randcycle! accept AbstractArray #58596

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4 changes: 4 additions & 0 deletions NEWS.md
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Expand Up @@ -61,6 +61,10 @@ Standard library changes

#### Profile

#### Random

* `randperm!` and `randcycle!` now support non-`Array` `AbstractArray` inputs, assuming they are mutable and their indices are one-based ([#58596]).

#### REPL

* The display of `AbstractChar`s in the main REPL mode now includes LaTeX input information like what is shown in help mode ([#58181]).
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20 changes: 14 additions & 6 deletions stdlib/Random/src/misc.jl
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Expand Up @@ -297,13 +297,16 @@ randperm(r::AbstractRNG, n::T) where {T <: Integer} = randperm!(r, Vector{T}(und
randperm(n::Integer) = randperm(default_rng(), n)

"""
randperm!([rng=default_rng(),] A::Array{<:Integer})
randperm!([rng=default_rng(),] A::AbstractArray{<:Integer})

Construct in `A` a random permutation of length `length(A)`. The
optional `rng` argument specifies a random number generator (see
[Random Numbers](@ref)). To randomly permute an arbitrary vector, see
[`shuffle`](@ref) or [`shuffle!`](@ref).

!!! compat "Julia 1.13"
`A isa Array` was required prior to Julia v1.13.

# Examples
```jldoctest
julia> randperm!(Xoshiro(123), Vector{Int}(undef, 4))
Expand All @@ -314,8 +317,9 @@ julia> randperm!(Xoshiro(123), Vector{Int}(undef, 4))
3
```
"""
function randperm!(r::AbstractRNG, a::Array{<:Integer})
function randperm!(r::AbstractRNG, a::AbstractArray{<:Integer})
# keep it consistent with `shuffle!` and `randcycle!` if possible
Base.require_one_based_indexing(a)
n = length(a)
@assert n <= Int64(2)^52
n == 0 && return a
Expand All @@ -332,7 +336,7 @@ function randperm!(r::AbstractRNG, a::Array{<:Integer})
return a
end

randperm!(a::Array{<:Integer}) = randperm!(default_rng(), a)
randperm!(a::AbstractArray{<:Integer}) = randperm!(default_rng(), a)


## randcycle & randcycle!
Expand Down Expand Up @@ -370,7 +374,7 @@ randcycle(r::AbstractRNG, n::T) where {T <: Integer} = randcycle!(r, Vector{T}(u
randcycle(n::Integer) = randcycle(default_rng(), n)

"""
randcycle!([rng=default_rng(),] A::Array{<:Integer})
randcycle!([rng=default_rng(),] A::AbstractArray{<:Integer})

Construct in `A` a random cyclic permutation of length `n = length(A)`.
The optional `rng` argument specifies a random number generator, see
Expand All @@ -382,6 +386,9 @@ which are sampled uniformly. If `A` is empty, `randcycle!` leaves it unchanged.

[`randcycle`](@ref) is a variant of this function that allocates a new vector.

!!! compat "Julia 1.13"
`A isa Array` was required prior to Julia v1.13.

# Examples
```jldoctest
julia> randcycle!(Xoshiro(123), Vector{Int}(undef, 6))
Expand All @@ -394,8 +401,9 @@ julia> randcycle!(Xoshiro(123), Vector{Int}(undef, 6))
1
```
"""
function randcycle!(r::AbstractRNG, a::Array{<:Integer})
function randcycle!(r::AbstractRNG, a::AbstractArray{<:Integer})
# keep it consistent with `shuffle!` and `randperm!` if possible
Base.require_one_based_indexing(a)
n = length(a)
@assert n <= Int64(2)^52
n == 0 && return a
Expand All @@ -411,4 +419,4 @@ function randcycle!(r::AbstractRNG, a::Array{<:Integer})
return a
end

randcycle!(a::Array{<:Integer}) = randcycle!(default_rng(), a)
randcycle!(a::AbstractArray{<:Integer}) = randcycle!(default_rng(), a)
8 changes: 8 additions & 0 deletions stdlib/Random/test/runtests.jl
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Expand Up @@ -554,6 +554,14 @@ end
@test randcycle!(mta, A) == randcycle!(mtb, B)
@test randcycle!(A) === A

@testset "non-`Array` `randperm!` and `randcycle!`" begin
x, y = Memory{Int}(undef, 10), Memory{Int}(undef, 10)
@test randperm!(mta, x) == randperm!(mtb, y)
@test randperm!(x) === x
@test randcycle!(mta, x) == randcycle!(mtb, y)
@test randcycle!(x) === x
end

let p = randcycle(UInt16(10))
@test typeof(p) ≡ Vector{UInt16}
@test sort!(p) == 1:10
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