[julia-users] Accessing a field in an immutable from an offset of the first field

[Kristoffer Carlsson]

Hello everyone.

Assume I have an immutable like:

immutable Foo{M, N, T}
   a::NTuple{M, T}
   b::NTuple{N, T}
end

and I want to make an efficient getindex into the tuple.

Something that would probably be inefficient due to branching would be:

function Base.getindex{M, N}(f::Foo({M,N}), i)
    if i <= M
       return f.a[i]
    else
       return f.b[i - N]
    end
end

Is there anyway I can just grab the value at the address at an offset i - 1 
further forward of the address of f.a[1]. In my head this would be more 
efficient since it would be a very simple offset calculation. You can 
assume that T is a nice bits type like a Float32.

Thanks!

// Kristoffer