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ocamlgraph ConcreteBidirectional and Dot
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Date: 2009-04-03 (12:37)
From: Pietro Abate <Pietro.Abate@p...>
Subject: ocamlgraph ConcreteBidirectional and Dot
Hello all.

I've a small problem with ocamlgraph.
I want to parse a dot graph into a ConcreteBidirectional.

The problem is that the signature needed for Dot.Parse requires a function
edge, but I've no mean to specify a label (since it is unlabelled !!)... 

The functor for ConcreteBidirectional says E.t = (V.t * V.t), 
but I don't quite understand the type of B.G.E.label ... 

ConcreteBidirectional is of type Sig.I with
with type V.t = V.t and type V.label = V.t and type E.t = V.t * V.t

Sig.I includes Sig.G

and Sig.G has E: Sig.EDGE  with type vertex = vertex
but I'm missing the type of label for unlabelled graphs ... that should be
an implementation detail, isn't it ?

I tried to look at the implementation of per_imp.ml but I got a bit lost...

this is what I'm trying to do: 

module V = struct
    type t = string
    let compare = Pervasives.compare
    let hash = Hashtbl.hash
    let equal l1 l2 = (l1 = l2)

module G = Imperative.Digraph.ConcreteBidirectional(V)

module B = Builder.I(G)

module L = struct
  open Dot_ast
  let node (id,_) attrs = match id with
    | Ident i -> i
    | Number n -> n
    | String s -> s
    | Html h -> h
  let edge l = ""

module DIn = Dot.Parse (B)(L)


the problem is:

Error: Signature mismatch:
       Modules do not match:
           val node : Graph.Dot_ast.id * 'a -> 'b -> string
           val edge : 'a -> string
       is not included in
           val node :
             Graph.Dot_ast.node_id -> Graph.Dot_ast.attr list -> B.G.V.label
           val edge : Graph.Dot_ast.attr list -> B.G.E.label
       Values do not match:
         val edge : 'a -> string
       is not included in
         val edge : Graph.Dot_ast.attr list -> B.G.E.label
Command exited with code 2.