Constructors for 2.0

[etiennedeg]

Here is a thread for discussing the constructors for Graphs 2.0

Current constructors

Constructors for SimpleGraph

• SimpleGraph{T}() : empty graph
• SimpleGraph{T}(nv::Integer) : graph with no edges
• SimpleGraph{T}(nv::Integer, ne::Integer) : random graph (erdos-renyi)
• SimpleGraph(::Type{T}) : empty graph
• SimpleGraph(nv::Integer, ne::Integer, edgestream::Channel) : add edges from the stream until stream end or we reach ne edges.
• SimpleGraphFromIterator(edgelist)
• SimpleGraph(adjmx::AbstractMatrix)
• SimpleGraph{T}(g::AbstractGraph)
• SimpleGraph(edge_list::Vector{SimpleGraphEdge{T}})

Goals for 2.0

We will have a new concrete graph type Graph{V} which can represent arbitrary vertices.
We would need new constructors to be able to construct such new graphs.

Instead of passing nv, we should provide a list (or even an iterator ?) of the vertices of the graph.

As the type of vertices can be arbitrary, the type signatures of generators can quickly become a mess / incompatible

Also we will need to support multigraphs

My proposal

• Graph{V}() and Graph(::Type{V})should be unambiguous
• Remove SimpleGraph{T}(nv::Integer, ne::Integer) (much better to call explicitly erdos-renyi)
• I don't really get this one SimpleGraph(nv::Integer, ne::Integer, edgestream::Channel), I think It does not add much to SimpleGraphFromIterator
• Keep Graph{T<:Integer}(nv::Integer)
• Use keywords for other generators:
  • Graph{V<:Integer}(adjmx=adjmx)
  • (Multi)Graph{V}(edge_list=edge_list)
  • (Multi)Graph{V}(vertices=vertices)
  • (Multi)Graph{V}(vertices=vertices::Vector{V})
  • Graph{V}(vertices=vertices::Vector{V}, adjmx=adjmx)
  • (Multi)Graph{V}(vertices=vertices::Vector{V}, edge_list=edge_list)

Is this proposal sound?
Do you have some other ideas of generators? A better proposal?