You need to either `import Base.start` or implement a function named
`Base.start` instead of `start`. That change will make your `start`
function extend the one from Base with new methods, rather than being a
separate function that happens to be named `start`. (This is a super common
confusion.)
-- Leah
On Sun, Jul 27, 2014 at 2:40 PM, Ben Ward <axolotlfan9...@gmail.com> wrote:
> I've given this a go but it does not quite work as expected:
>
> immutable DepthFirst
> tree::Phylogeny
> end
>
> function start(x::DepthFirst)
> state = Stack(PhyNode)
> push!(state, x.tree.Root)
> return state
> end
>
> function next(x::DepthFirst, state)
> current::PhyNode = pop!(state)
> for i in current.Children
> push!(state, i)
> end
> return current, state
> end
>
> function done(x::DepthFirst, state)
> return length(state) == 0 ? true : false
> end
>
> Then:
>
> *for i in DepthFirst(myTree)*
>
> *i*
>
> *end*
>
> results in:
>
> *ERROR: `start` has no method matching start(::DepthFirst)*
>
>
>
>
> * in anonymous at no file*
>
> I'm not sure why this is - I have a method defined start() for the
> utterable immutable DepthFirst trivial type. I'm clearly missing something
> here.
>
>
> On Sunday, July 27, 2014 7:58:09 PM UTC+1, Tim Holy wrote:
>>
>> Did you check out the examples I suggested? :)
>>
>> On Sunday, July 27, 2014 11:56:16 AM Ben Ward wrote:
>> > 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.
>>
>>
