Hey,

I want to implement a parametric type (container of defined length), i.e., something like `MyContainer{Int64, 2}([1, 1])`

should be a valid call to a constructor.

To me this looks very similar to the Array types (although they are only parameterized in terms of their dimensions).

The documentation on parametric types does not seem to cover this case explicitly and the Julia implementation of Arrays in the GitHub repos is a wee bit too abstract for me x)

My current solution appears a bit ‘hackish’ to me:

```
struct MyContainer{T,N}
values::Vector{T}
MyContainer{T,N}(values::Vector{T}) where{T,N} = isa(N, Int) & (N == length(values)) ? new(values) : error("")
end
MyContainer(values) = MyContainer{eltype(values),length(values)}(values)
MyContainer([1,1])
```

Is there a cleaner way of doing this?