Support for non-Int indices

General Usage
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1

What is the current level of support for array indices other than Int? other than Integer? What are the plans going forward to support (or not) these?

2

You can use non-integer indices but if you don’t have AbstractUnitRange axes then you can’t be a subtype of an AbstractArray and expect things to work. You can just be an indexable object that behaves mostly array-like.

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3

What are you trying to do with non-integer indices? What would they mean for an array?

(If you are trying to denote some kind of continuous interpolation probably it makes more sense to use f(x) than f[x]. But if you define your own type of f object you are free to define f[x] to do whatever you want by overloading Base.getindex.)

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4

Is this supposed to work?

struct Three <: AbstractVector{Int} end
Base.size(::Three) = (0x3,)
Base.axes(::Three) = (0x3:0x5,)
Base.getindex(::Three, ::UInt8) = 3

three = Three();

for x in three
    println(x)
end
# 3
# 3
# 3

for i in eachindex(three)
    println(three[i])
end
# 3
# 3
# 3

println(three)
# ERROR: CanonicalIndexError: getindex not defined for Three

I’m trying to test the limits of the language, be silly, and fool around :slight_smile:
Practically, I’m wondering what I’m allowed to assume about AbstractArrays and AbstractVectors when writing generic code.

5

you need to handle ::Int:

https://docs.julialang.org/en/v1/manual/interfaces/#man-interface-array

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