Consider the following function signature: function f(xs :: AbstractVector{T}, ::Val{U}, ::Val{V}) where {T, U, V}. I understand the concept of value types, but I'm not certain if I understand the meaning of the prepended double-colon and I can't seem to be able to find any information specifically on this subject.
In C++ similar syntax would ensure that resolution of the name occurs from the global instead of current namespace but I'm not sure this applies to Julia (and, if it does, how). I can infer that this has to do with types since the same syntax is used to denote the type of a variable but what does it mean to have a type assignment without the assignee? TIA.
function f(xs :: AbstractVector{T}, ::Val{U}, ::Val{V}) where {T, U, V}
means that the call to f must pass three arguments of types AbstractVector, Val and Val respectively. However, you capture the value of passed variable only for the first argument xs. The values of the second and third arguments are not captured (in this case you do not really need them as Val is a singleton type). But you capture types T, U and V, and can refer to them in the body of the function.