View the shortest paths

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Info about a graph with structure...

Daniele Carlucci

13 Jul 2004 13 Jul '04

4:52 p.m.

Hi, Which is the command to visualize a path in a graph? For ie I want to visualize all the shortest path inside a graph, or all the path from a source to a dest. Thanks Daniele

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Doug Gregor

14 Jul 14 Jul

2:26 p.m.

On Jul 13, 2004, at 11:52 AM, Daniele Carlucci wrote:

...

Hi, Which is the command to visualize a path in a graph? For ie I want to visualize all the shortest path inside a graph, or all the path from a source to a dest.

There is no direct way to visualize a graph with the Boost Graph Library. You can get the paths by supplying a "predecessor_map" parameter to Dijkstra's algorithm and rebuilding the path from the predecessor tree. Doug

Delfin Rojas

20 Jul 20 Jul

12:15 a.m.

New subject: Mpl problem

Hi there, I am having a problem with the mpl library and I wonder if someone could help me with it. Basically I am trying to get a joint_view of two mpl::vector types and I get an error message on mpl/clear.hpp saying clear_traits< Tag > ::template algorithm< Sequence > base class undefined. I tried including several of the mpl hpp files, the ones that seemed could have something to do with this problem but that didn't help. I also get a similar problem trying to use mpl::push_back. In this case I get push_back_traits< Tag > ::template algorithm< Sequence,T > Base class undefined. On the other hand mpl::push_front and mpl::insert compile beautifully. Any ideas? Thanks -delfin

Arkadiy Vertleyb

12:50 a.m.

New subject: Mpl problem

"Delfin Rojas" wrote

...

I am having a problem with the mpl library and I wonder if someone could help me with it. Basically I am trying to get a joint_view of two mpl::vector types and I get an error message on mpl/clear.hpp saying

clear_traits< Tag > ::template algorithm< Sequence >

base class undefined.

I tried including several of the mpl hpp files, the ones that seemed could have something to do with this problem but that didn't help. I also get a similar problem trying to use mpl::push_back. In this case I get

push_back_traits< Tag > ::template algorithm< Sequence,T >

Base class undefined.

On the other hand mpl::push_front and mpl::insert compile beautifully.

The error messages you are getting basically say: "This algorithm is undefined for this type of sequence." I never used joint_view, but the push_back is currently not defined for the mpl::vector. AFAIK, this is going to be corrected in the next version of Boost (which is currently being put together). Also, if you are trying to use push_back in combination with, say, fold, this can be replaced with push_front in combination with fold_backward. HTH, Arkadiy

David Abrahams

2:54 a.m.

New subject: Mpl problem

"Arkadiy Vertleyb" writes:

...

"Delfin Rojas" wrote

...
I am having a problem with the mpl library and I wonder if someone could help me with it. Basically I am trying to get a joint_view of two mpl::vector types and I get an error message on mpl/clear.hpp saying

clear_traits< Tag > ::template algorithm< Sequence >

base class undefined.

I tried including several of the mpl hpp files, the ones that seemed could have something to do with this problem but that didn't help. I also get a similar problem trying to use mpl::push_back. In this case I get

push_back_traits< Tag > ::template algorithm< Sequence,T >

Base class undefined.

On the other hand mpl::push_front and mpl::insert compile beautifully.

The error messages you are getting basically say:

"This algorithm is undefined for this type of sequence."

Delfin Rojas

7:24 p.m.

New subject: Mpl problem

Hi David, I wasn't trying to add elements to a joint view. I am trying to make a joint sequence of two other sequences. I first tried to obtain that from joint_view but when that failed I tried using push_back to push each element of the second sequence at the end of the first one. I thought about trying mpl::copy but I am not sure if that is implemented either... Thanks -delfin -----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of David Abrahams Sent: Monday, July 19, 2004 7:55 PM To: boost-users@lists.boost.org Subject: [Boost-users] Re: Mpl problem "Arkadiy Vertleyb" writes:

...

"Delfin Rojas" wrote

...
I am having a problem with the mpl library and I wonder if someone could help me with it. Basically I am trying to get a joint_view of two mpl::vector types and I get an error message on mpl/clear.hpp saying

clear_traits< Tag > ::template algorithm< Sequence >

base class undefined.

I tried including several of the mpl hpp files, the ones that seemed could have something to do with this problem but that didn't help. I also get a similar problem trying to use mpl::push_back. In this case I get

push_back_traits< Tag > ::template algorithm< Sequence,T >

Base class undefined.

On the other hand mpl::push_front and mpl::insert compile beautifully.

The error messages you are getting basically say:

"This algorithm is undefined for this type of sequence."

Exactly. Like all other views, joint_view is not extensible. How could you push_back onto a view, anyway? push_back is supposed to return the same "kind" of sequence as its input, but you can't add an element to a joint_view. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

David Abrahams

7:40 p.m.

New subject: Mpl problem

"Delfin Rojas" writes:

...

Hi David,

I wasn't trying to add elements to a joint view. I am trying to make a joint sequence of two other sequences.

mpl::joint_view that's all you need to do.

...

I first tried to obtain that from joint_view but when that failed I tried using push_back to push each element of the second sequence at the end of the first one. I thought about trying mpl::copy but I am not sure if that is implemented either...

This problem:

...

...
...
I am having a problem with the mpl library and I wonder if someone could help me with it. Basically I am trying to get a joint_view of two mpl::vector types and I get an error message on mpl/clear.hpp saying

clear_traits< Tag > ::template algorithm< Sequence >

base class undefined.

Can only occur by trying to extend the joint_view, if it's caused when you're "trying to make a joint view". -- Dave Abrahams Boost Consulting http://www.boost-consulting.com

Delfin Rojas

7:21 p.m.

New subject: Mpl problem

Thanks for the explanation Arkadiy. I had the impression this was probably a problem of stuff not been implemented yet. However since mpl documentation talks about vector and push_back I thought it was there... What I'm trying to do is make a variant that is a superset of another variant. For that, I make an initial mpl sequence with the types of the first variant and create it. Then I make a second list with the extra types of the second variant. I would then like to create the second variant passing the joint list of the first types sequence and second types sequence. That is why I wanted to use joint_view. Then I thought I would just push_back each of the second variant types to the first types sequence but that failed too. Finally I am doing an insert at the end (essentially a push_back but not quite). Thanks again -delfin -----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Arkadiy Vertleyb Sent: Monday, July 19, 2004 5:51 PM To: boost-users@lists.boost.org Subject: [Boost-users] Re: Mpl problem "Delfin Rojas" wrote

...

I am having a problem with the mpl library and I wonder if someone could help me with it. Basically I am trying to get a joint_view of two mpl::vector types and I get an error message on mpl/clear.hpp saying

clear_traits< Tag > ::template algorithm< Sequence >

base class undefined.

I tried including several of the mpl hpp files, the ones that seemed could have something to do with this problem but that didn't help. I also get a similar problem trying to use mpl::push_back. In this case I get

push_back_traits< Tag > ::template algorithm< Sequence,T >

Base class undefined.

On the other hand mpl::push_front and mpl::insert compile beautifully.

Arkadiy Vertleyb

7:49 p.m.

New subject: Mpl problem

"Delfin Rojas" wrote

...

What I'm trying to do is make a variant that is a superset of another variant. For that, I make an initial mpl sequence with the types of the first variant and create it. Then I make a second list with the extra types of the second variant. I would then like to create the second variant passing the joint list of the first types sequence and second types sequence. That is why I wanted to use joint_view. Then I thought I would just push_back each of the second variant types to the first types sequence but that failed too. Finally I am doing an insert at the end (essentially a push_back but not quite).

If you just need to concatenate two sequences, you can use fold_backward and push_front, something like: template struct concatenate : mpl::fold_backward< V1, V2, mpl::push_front<_,_> // please verify this -- not sure about the order -- may be <_2, _1>

...

{};

HTH, Arkadiy

Arkadiy Vertleyb

8:08 p.m.

New subject: Mpl problem

"Arkadiy Vertleyb" wrote

...

If you just need to concatenate two sequences, you can use fold_backward and push_front, something like:

template struct concatenate : mpl::fold_backward< V1, V2, mpl::push_front<_,_> // please verify this -- not sure about the order -- may be <_2, _1>

...
{};

After taking a look at the joint_view documentation:

...

Complexity Amortized constant time.

... I actually regret that I ever suggested using fold_backward/push_front for this purpose :) Arkadiy

David Abrahams

8:48 p.m.

New subject: Mpl problem

"Arkadiy Vertleyb" writes:

...

If you just need to concatenate two sequences, you can use fold_backward and push_front, something like:

template struct concatenate : mpl::fold_backward< V1, V2, mpl::push_front<_,_> // please verify this -- not sure about the order -- may be <_2, _1>

...
{};

That's a lot costlier than using joint_view, though. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com

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participants (5)

Arkadiy Vertleyb
Daniele Carlucci
David Abrahams
Delfin Rojas
Doug Gregor