use ~ instead of - plus unsigned to obtain positive numbers

stdlib/Random/src/RNGs.jl

@@ -303,15 +303,12 @@ This is an internal function, subject to change.
 """
 function make_seed(n::Integer)
  neg = signbit(n)
- n = abs(n) # n can still be negative, e.g. n == typemin(Int)
- if n < 0
- # we assume that `unsigned` can be called on integers `n` for which `abs(n)` is
- # negative; `unsigned` is necessary for `n & 0xffffffff` below, which would
- # otherwise propagate the sign bit of `n` for types smaller than UInt32
- n = unsigned(n)
+ if neg
+ n = ~n
  end
+ @assert n >= 0
  seed = UInt32[]
- # we directly encode the bit pattern of `abs(n)` into the resulting vector `seed`;
+ # we directly encode the bit pattern of `n` into the resulting vector `seed`;
  # to greatly limit breaking the streams of random numbers, we encode the sign bit
  # as the upper bit of `seed[end]` (i.e. for most positive seeds, `make_seed` returns
  # the same vector as when we didn't encode the sign bit)
@@ -333,7 +330,7 @@ function from_seed(a::Vector{UInt32})::BigInt
  neg = !iszero(a[end] & 0x80000000)
  seed = sum((i == length(a) ? a[i] & 0x7fffffff : a[i]) * big(2)^(32*(i-1))
  for i in 1:length(a))
- neg ? -seed : seed
+ neg ? ~seed : seed
 end
 
 

stdlib/Random/src/Xoshiro.jl

@@ -4,7 +4,7 @@
 # Lots of implementation is shared with TaskLocalRNG
 
 """
- Xoshiro(seed)
+ Xoshiro(seed::Integer)
  Xoshiro()
 
 Xoshiro256++ is a fast pseudorandom number generator described by David Blackman and
@@ -21,7 +21,6 @@ multiple interleaved xoshiro instances).
 The virtual PRNGs are discarded once the bulk request has been serviced (and should cause
 no heap allocations).
 
-The `seed` may be an integer or a vector of `UInt32` integers.
 If no seed is provided, a randomly generated one is created (using entropy from the system).
 See the [`seed!`](@ref) function for reseeding an already existing `Xoshiro` object.
 
@@ -98,7 +97,7 @@ Using or seeding the RNG of any other task than the one returned by `current_tas
 is undefined behavior: it will work most of the time, and may sometimes fail silently.
 
 When seeding `TaskLocalRNG()` with [`seed!`](@ref), the passed seed, if any,
-may be an integer or a vector of `UInt32` integers.
+may be any integer.
 
 !!! compat "Julia 1.11"
  Seeding `TaskLocalRNG()` with a negative integer seed requires at least Julia 1.11.