iterating elements

[filchristou]

I find iterating through the elements of a MetaGraph hard.
For the docs example:

julia> colors = MetaGraph( Graph(), VertexData = String, EdgeData = Symbol, graph_data = "graph_of_colors")
Meta graph based on a {0, 0} undirected simple Int64 graph with vertex labels of type Symbol, vertex metadata of type String, edge metadata of type Symbol, graph metadata given by "graph_of_colors", and default weight 1.0
julia> colors[:red] = "warm";
julia> colors[:yellow] = "warm";
julia> colors[:blue] = "warm";  # wrong metadata
julia> colors[:blue] = "cool";
julia> colors[:red, :yellow] = :orange;
julia> colors[:red, :blue] = :violet;
julia> colors[:yellow, :blue] = :green;

I would do

julia> [colors[label_for(colors,v)] for v in vertices(colors)]
3-element Vector{String}:
 "warm"
 "warm"
 "cool"

which is a little bit tedious to write and I would love some syntactic sugar like:

[get_vertex(colors, v) for v in vertices(colors)]

The iteration of edges is even more tedious to write:

julia> [colors[label_for(colors, e.src), label_for(colors, e.dst)] for e in edges(colors)]
3-element Vector{Symbol}:
 :orange
 :violet
 :green

Ofc it's also ridiculously simple to write such functions alone, but I think such functionality should be provided from the library.

Or is there another easier to way to iterate MetaGraph elements already ?

[filchristou]

Locally I create a function which returns all the node-data like following:

julia> get_vertices(x) = getindex.(values(x.vertex_properties), 2)
julia> get_vertices(colors)
3-element Vector{String}:
 "warm"
 "warm"
 "cool"

[bramtayl]

Well, you can use the fields of the objects directly, but that's not really a public interface. I agree, a public interface would be nice. Maybe something like

EdgeIterator which would collect to

[:blue => "cool", :red => "warm", :yellow => "warm"]

and

VertexIterator which would collect to

[(:red, :yellow) => :orange, (:red, :blue) => :violet, (:yellow, :blue) => :green)]

?

`

[filchristou]

Probably you meant it the other way around, but yes, something like that would prevent boilerplate code.

[gdalle]

Well, you can use the fields of the objects directly, but that's not really a public interface. I agree, a public interface would be nice. Maybe something like

EdgeIterator which would collect to

[:blue => "cool", :red => "warm", :yellow => "warm"]

and

VertexIterator which would collect to

[(:red, :yellow) => :orange, (:red, :blue) => :violet, (:yellow, :blue) => :green)]

?

`

This sounds good, gonna take a look

[gdalle]

Related: #39 and #44

[gdalle]

#45 added a labels function

[gdalle]

We should also add edge_labels and (in/out)neighbor_labels

[gdalle]

And make sure that the order is coherent with the iterators vertices, edges and (in/out)neighbors

[gdalle]

thanks @thchr

[gdalle]

Solved by #50