On Wednesday, April 8, 2015 at 8:00:42 AM UTC-7, Tim Holy wrote:
>
> It's a matter of taste, really, but in general I agree that the Julian way
> is
> to reduce the number of accesses to fields directly. That said, I do
> sometimes
> access the fields.
>
> However, your iterator example is a good opportunity to illustrate a more
> julian approach:
>
> mesh = mesh(...)
> for vertex in vertices(mesh)
> blah blah
> end
>
> The idea is that vertices(mesh) might return an iterator object, and then
> you
> write start, next, and done functions to implement iteration. Presumably
> you
> should build the iterators for Mesh on top of iterators for FESection,
> etc, so
> the whole thing is composable. You'd then have short implementations of
> the
> vertices function taking a Mesh, FESection, or Element.
>
>
Tim,
Can you comment on the performance implications of directly accessing
fields vs your approach? I'm guessing that directly accessing the fields
would be faster?
Phil
> On Wednesday, April 08, 2015 06:35:46 AM Kristoffer Carlsson wrote:
> > I come from a Python background where direct access to fields in for
> > example classes with the dot notation is very common.
> >
> > However, from what I have seen in different conversations, accessing
> fields
> > directly is not really Julian. Sort of a "fields are an implementation
> > detail" mindset, and "what is important are the functions".
> >
> > Here is an example of a type hierarchy that is a little bit similar to
> > types I am working with now:
> >
> > type Element
> > vertices::Vector{Int}
> > end
> >
> > type Node
> > coordinates::Vector{Float64}
> > id::Int
> > end
> >
> > type FESection
> > elements::Vector{Elements}
> > nodes::Vector{Nodes}
> > end
> >
> > type Mesh
> > sections::Vector{FESection}
> > end
> >
> > Now, let's say that I want to write a function to loop over all
> vertices.
> > One way (which I would do in Python is):
> >
> > mesh = Mesh(.....)
> > for section in mesh.sections
> > for element in section.elements
> > for vertices in element.vertices
> > blah bla
> > end
> > end
> > end
> >
> >
> >
> > However, this accesses the fields directly. Would it be more Julian to
> > write getters for the fields? Since Julia does not have @property like
> > Python I realize that by accessing the fields you commit to exactly the
> > name of the field and it's type while with a getter it would be more
> > flexible.
> >
> > Best regards,
> > Kristoffer Carlsson
>
>
