Re: [Boost-users] [bgl] depth_first_search does not compile. color_map howto?

Subject: Re: [Boost-users] [bgl] depth_first_search does not compile. color_map howto?
From: Joachim Faulhaber (afojgo_at_[hidden])
Date: 2012-07-04 05:10:31

2012/6/29 Jeremiah Willcock <jewillco_at_[hidden]>:
> On Fri, 29 Jun 2012, Joachim Faulhaber wrote:
>
>> Dear Jeremiah,
>>
>> thank you for your answer. Unfortunately, it doesn't solve my
>> problems. I admit, I am pretty much frustrated with BGL usability.
>> Generally I am fond of boost and I recommend using it to my
>> colleagues. But currently my experiences with BGL is very
>> unsatisfactory. I hope there are solutions.
>
>
> BGL can be quite frustrating to use, especially since diagnosis of
> errors is not always good.  The trunk version should be better by a
> little bit, but it still does require some experience to track down
> errors.
>
>
>> 2012/6/28 Jeremiah Willcock <jewillco_at_[hidden]>:
>>>
>>> On Mon, 25 Jun 2012, Joachim Faulhaber wrote:
>>>
>>>> Hi,
>>>>
>>>> When using visitors with the depth_first_search algorithm I can
>>>> successfully compile and run this code:
[...]
>>>
>>> The simplest way is probably to use associative_property_map; see lines
>>> 129-140 of
>>>
>>> http://www.informatik.uni-koeln.de/scil/documentation/html/SteinerArborescence_8cc_source.html
>>> for an example.  You can also look at
>>>
>>> http://boost.2283326.n4.nabble.com/BGL-dijkstra-shortest-paths-with-listS-td2557281.html
>>> for other places where associative_property_map can be used.
[...]
>>> From your recommendation ...
>>
>>> The simplest way is probably to use associative_property_map; see lines
>>> 129-140 of
>>>
>>> http://www.informatik.uni-koeln.de/scil/documentation/html/SteinerArborescence_8cc_source.html
>>
>> ... I have tried to fix my example:
>>
>> //=========================================================
>> template<class Graph>
>> class Visitor: public default_dfs_visitor
>> {
>> public:
>>  typedef typename
>>    graph_traits<Graph>::vertex_descriptor Vertex;
>>
>>  void discover_vertex(Vertex v, const Graph& g)const
>>  {cout << v << " "; return;}
>> };
>>
>> struct Int{
>>  Int(): _value(0){}
>>  Int(int val): _value(val){}
>>  int _value;
>> };
>>
>> void GLL_visit()
>> {
>>  typedef adjacency_list<listS, listS, directedS, Int> GraphLL;
>>  typedef graph_traits<GraphLL>::vertex_descriptor VertexLL;
>>  typedef graph_traits<GraphLL>::vertex_iterator vertex_iter;
>>
>>  //Add an associative color map type.
>>  typedef map<VertexLL, default_color_type> color_map_t;
>>  color_map_t color_map; //Declare a container
>>
>>  GraphLL g; //Graph and color_map should fit.
>>  //Fill graph g
>>  VertexLL v0 = boost::add_vertex(g);
>>  VertexLL v1 = boost::add_vertex(g);
>>  g[v0] = Int(0);
>>  g[v1] = Int(1);
>>  add_edge(v0, v1, g);
>>
>>  //Intitalize the colormap
>>  BGL_FORALL_VERTICES(v, g, GraphLL) {
>>    color_map[v] = white_color;
>>  }
>>  //Generate an assoc property map
>>  associative_property_map<color_map_t> pm_color(color_map);
>>
>>  Visitor<GraphLL> vis;
>>  //Again compiler errors here:
>>  boost::depth_first_search(g, visitor(vis), pm_color); //(*)
>
>
> You are mixing named parameters and positional parameters -- try either:
>
> boost::depth_first_search(g, vis, pm_color);
>
> or:
>
> boost::depth_first_search(g, visitor(vis).color_map(pm_color));
>
> and see if either of those work.

yes, this was it! Thanks for the answer.

This is little trap one can fall into. When extending examples from
the documentation using different overloads of an algorithm it is easy
to overlook that parameter types are changing from 'named' to
'positional' mode...

Thanks for helping :)

Cheers,
Joachim

-- 
Interval Container Library [Boost.Icl]
http://www.joachim-faulhaber.de