Start Bi-infinite ranges

Author: dlfivefifty

src/InfiniteArrays.jl

@@ -211,7 +211,7 @@ end
     return LazyArrays.searchsortedlast_recursive(n, x, args...)
 end
 
-
+include("biinfrange.jl")
 
 
 end # module

src/biinfrange.jl

@@ -0,0 +1,21 @@
+"""
+BiInfUnitRange()
+
+Represent -∞:∞ with offset indexing
+"""
+struct BiInfUnitRange{T<:Real} <: AbstractInfUnitRange{T} end
+
+BiInfUnitRange() = BiInfUnitRange{Int}()
+
+AbstractArray{T}(a::BiInfUnitRange) where T<:Real = BiInfUnitRange{T}(a)
+AbstractVector{T}(a::BiInfUnitRange) where T<:Real = BiInfUnitRange{T}(a)
+
+unitrange(a::BiInfUnitRange) = a
+Base.has_offset_axes(::BiInfUnitRange) = true
+
+getindex(v::BiInfUnitRange{T}, i::Integer) where T = convert(T, i)
+axes(::BiInfUnitRange) = (BiInfUnitRange(),)
+first(::BiInfUnitRange) = -∞
+show(io::IO, ::BiInfUnitRange{Int}) = print(io, "BiInfUnitRange()")
+
+getindex(r::BiInfUnitRange{T}, s::AbstractUnitRange{<:Integer}) where T = convert(AbstractVector{T}, s)

test/test_biinfrange.jl

@@ -0,0 +1,8 @@
+using InfiniteArrays, Base64, Test
+using InfiniteArrays: BiInfUnitRange
+
+@testset "-∞:∞" begin
+    r = BiInfUnitRange()
+    @test stringmime("text/plain", r) == "BiInfUnitRange()"
+    
+end