I had not considered this - so state variable is a complex type which would
have say the Queue/Stack and current value, and the start, next and done
methods update it?
On Sunday, July 27, 2014 7:48:56 PM UTC+1, Tim Holy wrote:
>
> Why can't you keep track of everything in the state variable, and make
> your
> iterator-types trivial?
>
> --Tim
>
> On Sunday, July 27, 2014 11:07:36 AM Ben Ward wrote:
> > My traverser types are not exactly wrappers quite a simple as they
> contain
> > FIFO and FILO structures that keep track of things - I struggle to
> imagine
> > how else to have them. Do the three iterate methods necessarily need to
> > have the second argument "state"? My types know they are done -
> > hasReachedEnd() - because there are no more nodes to visit in their
> Ahead
> > Queue/Stack. So would a done() that only requires the type be sufficient
> > with no state input variable as in done(tier, state)?
> >
> > Best,
> > Ben.
> >
> > On Sunday, July 27, 2014 4:49:24 PM UTC+1, Tim Holy wrote:
> > > You can obtain different types of iteration simply by wrapping "obj"
> in
> > > different thin-wrappers. For example, you can define
> > >
> > > immutable SomeOtherWayOfTraversing{T}
> > >
> > > obj::T
> > >
> > > end
> > >
> > > which is used as
> > >
> > > for x in SomeOtherWayOfTraversing(obj)
> > >
> > > # blah
> > >
> > > end
> > >
> > > and then write the specific start, next, done methods like this:
> > >
> > > start{T}(iter::SomeOtherWayOfTraversing{T})
> > >
> > > You can get totally different behavior this way from what would happen
> > > when you
> > > just say "for x in obj...".
> > >
> > >
> > > You might want to browse through more packages to see more examples.
> > > Here's
> > > one:
> > >
> > >
> https://github.com/timholy/Grid.jl/blob/600cbcf645a73525fb6d563d5a148b9d8b
> > > 2668aa/src/counter.jl but many other packages (DataFrames, Gtk, HDF5,
> etc)
> > > define iterators.
> > >
> > > --Tim
> > >
> > > On Sunday, July 27, 2014 06:41:43 AM Ben Ward wrote:
> > > > I'm not nessecerily trying it iterate over the children of a node.
> > >
> > > Rather I
> > >
> > > > have defined a series of types that facilitate traversing a tree in
> > >
> > > various
> > >
> > > > ways for my Phylogenetics.jl package, for example by depth first:
> > > >
> > > > type TraverserCore
> > > >
> > > > Start::PhyNode
> > > > Behind::Stack
> > > > History::Array{PhyNode, 1}
> > > > Current::PhyNode
> > > >
> > > > end
> > > >
> > > >
> > > > type DepthFirstTraverser <: TreeTraverser
> > > >
> > > > Ahead::Stack
> > > > Core::TraverserCore
> > > > function DepthFirstTraverser(tree::Phylogeny)
> > > >
> > > > x = new(Stack(PhyNode), TraverserCore(tree.Root, Stack(PhyNode),
> > >
> > > PhyNode
> > >
> > > > [], tree.Root))
> > > >
> > > > for i in x.Core.Current.Children
> > > >
> > > > push!(x.Ahead, i)
> > > >
> > > > end
> > > > return x
> > > >
> > > > end
> > > >
> > > > end
> > > >
> > > >
> > > > It has methods like:
> > > >
> > > >
> > > > function next!(x::DepthFirstTraverser)
> > > >
> > > > push!(x.Core.Behind, x.Core.Current)
> > > > x.Core.Current = pop!(x.Ahead)
> > > > for i in x.Core.Current.Children
> > > >
> > > > push!(x.Ahead, i)
> > > >
> > > > end
> > > >
> > > > end
> > > >
> > > >
> > > > function getCurrent(x::TreeTraverser)
> > > >
> > > > return x.Core.Current
> > > >
> > > > end
> > > >
> > > >
> > > > function hasReachedEnd(x::TreeTraverser)
> > > >
> > > > length(x.Ahead) > 0 ? false : true
> > > >
> > > > end
> > > >
> > > >
> > > > Which seem similar to start, next, and done. I'd use them in a loop
> like
> > >
> > > so
> > >
> > > > again from Phylogenetics.jl:
> > > >
> > > > while true
> > > >
> > > > show(getCurrent(traverser))
> > > > if hasReachedEnd(traverser)
> > > >
> > > > break
> > > >
> > > > end
> > > > next!(traverser)
> > > >
> > > > end
> > > >
> > > > But I'd like to make it behave more like an iterator - so be able to
> > >
> > > define
> > >
> > > > the iterator methods for it so I can do something like
> > > >
> > > > for i = DepthFirstTraverser(myTree)
> > > > # BLARGH
> > > > end
> > > >
> > > > And it will be translated accordingly. I think this is doable by
> > >
> > > defining
> > >
> > > > the three methods, making use of the types the method already has.
> > > >
> > > > The idea is to have a load of types that allow the user to code
> > >
> > > iteration
> > >
> > > > over the tree in any possible way, easily, providing there is a
> > > > TreeTraverser type for it.
> > > >
> > > > Best,
> > > > Ben.
> > > >
> > > > On Sunday, July 27, 2014 2:14:38 PM UTC+1, Tim Holy wrote:
> > > > > for x in obj
> > > > >
> > > > > # blah
> > > > >
> > > > > end
> > > > >
> > > > > will iterate if you've defined start, next, and done functions for
> > >
> > > which
> > >
> > > > > the
> > > > > first argument has typeof(obj). In your case you'd presumably use
> a
> > >
> > > node
> > >
> > > > > as
> > > > > obj, and the traversal would be recursively over all children of
> that
> > > > > node.
> > > > >
> > > > > If you want a specific tree example, check out
> > >
> > > ProfileView.jl/src/tree.jl.
> > >
> > > > > Best,
> > > > > --Tim
> > > > >
> > > > > On Sunday, July 27, 2014 05:13:39 AM Ben Ward wrote:
> > > > > > Hi,
> > > > > >
> > > > > > I've been writing a type for recursive tree structures, and
> several
> > > > >
> > > > > types
> > > > >
> > > > > > that traverse that tree in various manners like breadth first or
> > >
> > > depth
> > >
> > > > > > first. They have their own methods for getting the current tree
> > >
> > > node,
> > >
> > > > > > moving to the next node, whether an end has been reached and so
> on.
> > >
> > > The
> > >
> > > > > > contain fields for the nodes several steps ahead, those past
> etc. I
> > > > > > wondered if I might make it so as these types might easier be
> used
> > >
> > > in
> > >
> > > > > loops
> > > > >
> > > > > > by giving them the iterator protocol methods? I've not seen how
> to
> > > > >
> > > > > define
> > > > >
> > > > > > custom operators, is it as simple as defining start next and
> done?
> > >
> > > How
> > >
> > > > > is
> > > > >
> > > > > > the current value gotten? I guess its returned by next().
> > > > > >
> > > > > > Thanks,
> > > > > > Ben.
>
>
