add DummyEdgeMap and make it default

src/LightGraphs.jl

@@ -23,9 +23,9 @@ catch
 end
 
 import Base: write, ==, <, *, isless, issubset, complement, union, intersect,
-            reverse, reverse!, blkdiag, getindex, show, print, copy, in,
+            reverse, reverse!, blkdiag, getindex, setindex!, show, print, copy, in,
             sum, size, sparse, eltype, length, ndims, issym, transpose,
-            ctranspose, join, start, next, done, eltype
+            ctranspose, join, start, next, done, eltype, get
 
 
 # core

src/traversals/bfs.jl

@@ -49,7 +49,7 @@ function traverse_graph!(
     source,
     visitor::SimpleGraphVisitor;
     vertexcolormap = zeros(Int, nv(graph)),
-    edgecolormap = Dict{Edge, Int}(),
+    edgecolormap = DummyEdgeMap(),
     queue = Vector{Int}())
 
     for s in source

src/traversals/dfs.jl

@@ -59,7 +59,7 @@ function traverse_graph!(
     s::Int,
     visitor::SimpleGraphVisitor;
     vertexcolormap = zeros(Int, nv(graph)),
-    edgecolormap = Dict{Edge, Int}())
+    edgecolormap = DummyEdgeMap())
 
     vertexcolormap[s] = 1
     discover_vertex!(visitor, s) || return

src/traversals/graphvisit.jl

@@ -28,6 +28,15 @@ end
 # This is the common base for BreadthFirst and DepthFirst
 abstract SimpleGraphVisitAlgorithm
 
+type DummyEdgeMap
+end
+
+getindex(d::DummyEdgeMap, e::Edge) = 0
+setindex!(d::DummyEdgeMap, x, e::Edge) = x
+get(d::DummyEdgeMap, e::Edge, x) = x
+
+
+
 
 ###########################################################
 #