# This file is a part of Julia. License is MIT: https://julialang.org/license

# InfiniteArrays (arrays with infinite size)

# This test file is designed to exercise support for generic sizing,
# even though infinite arrays aren't implemented in Base.

module InfiniteArrays

export OneToInf, Infinity

"""
   Infinity()

represents infinite cardinality. Note that `Infinity <: Integer` to support
being treated as an index.
"""
struct Infinity <: Integer end

Base.:(==)(::Infinity, ::Int) = false
Base.:(==)(::Int, ::Infinity) = false
Base.:(<)(::Int, ::Infinity) = true
Base.:(≤)(::Int, ::Infinity) = true
Base.:(≤)(::Infinity, ::Int) = false
Base.:(≤)(::Infinity, ::Infinity) = true
Base.:(-)(::Infinity, ::Int) = Infinity()
Base.:(+)(::Infinity, ::Int) = Infinity()
Base.:(:)(::Infinity, ::Infinity) = 1:0

"""
    OneToInf(n)

Define an `AbstractInfUnitRange` that behaves like `1:∞`, with the added
distinction that the limits are guaranteed (by the type system) to
be 1 and ∞.
"""
struct OneToInf{T<:Integer} <: AbstractUnitRange{T} end

OneToInf() = OneToInf{Int}()

Base.axes(r::OneToInf) = (r,)
Base.unsafe_indices(r::OneToInf) = (r,)
Base.unsafe_length(r::OneToInf) = Infinity()
Base.size(r::OneToInf) = (Infinity(),)
Base.first(r::OneToInf{T}) where {T} = oneunit(T)
Base.length(r::OneToInf{T}) where {T} = Infinity()
Base.last(r::OneToInf{T}) where {T} = Infinity()
Base.unitrange(r::OneToInf) = r
Base.oneto(::Infinity) = OneToInf()

end