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Today's Topics:
1. Doing a DFS from scratch .... (Claudio Cesar de Sa)
2. Re: Doing a DFS from scratch .... (Ut Primum)
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Message: 1
Date: Tue, 20 Oct 2020 19:36:08 -0300
From: Claudio Cesar de Sa <ccs1...@gmail.com>
To: beginners@haskell.org
Subject: [Haskell-beginners] Doing a DFS from scratch ....
Message-ID:
<cahqhj4pr2xn+g833lix3uxmd29ueqqs0+pwgnpzowvs5ku1...@mail.gmail.com>
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Hi everyone
Initially, I hope that this list is active yet. For some days,
I had been trying to do a Depth First Search on a graph from scratch
following something very didactical (clear, elegant - legible, any worry
about efficiency).
This DFS keeps a boolean list to mark the nodes already visited and another
with current or valid nodes ( the stack of DFS classic).
The code is naive and well documented and is here:
https://github.com/claudiosa/CCS/blob/master/haskell/dfs_graph.hs
(excessively commented)
but unfortunately, it is not working. My guess is that the problem starts
on *new_node* function. I am not sure if in DFS, when a current node gets
a next neighbour to stack, it gets all the neighbours.
In this code, it is getting one node per time.
The functions next_node and one_node seem very non-sense. Could someone
help me?
Thanks in advance
claudio
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Message: 2
Date: Wed, 21 Oct 2020 08:52:54 +0200
From: Ut Primum <utpri...@gmail.com>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <beginners@haskell.org>
Subject: Re: [Haskell-beginners] Doing a DFS from scratch ....
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Hi Claudio,
I had a look at the code, and it looks that in dfs_search function, where
the comment says that "BACTRACKING is happening HERE" there is something
wrong (it looks neighbours are not all considered, because as you said
next_node returns only one neighbour).
I think that the definition of
dfs_search (x:xs) l_closed
is wrong. I'd start to write it from the beginning, instead of correcting
this code.
Cheers,
Ut
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Il giorno mer 21 ott 2020 alle ore 00:37 Claudio Cesar de Sa <
ccs1...@gmail.com> ha scritto:
> Hi everyone
>
> Initially, I hope that this list is active yet. For some days,
> I had been trying to do a Depth First Search on a graph from scratch
> following something very didactical (clear, elegant - legible, any worry
> about efficiency).
>
> This DFS keeps a boolean list to mark the nodes already visited and
> another with current or valid nodes ( the stack of DFS classic).
>
> The code is naive and well documented and is here:
>
> https://github.com/claudiosa/CCS/blob/master/haskell/dfs_graph.hs
> (excessively commented)
>
> but unfortunately, it is not working. My guess is that the problem
> starts on *new_node* function. I am not sure if in DFS, when a current
> node gets a next neighbour to stack, it gets all the neighbours.
> In this code, it is getting one node per time.
>
> The functions next_node and one_node seem very non-sense. Could someone
> help me?
>
> Thanks in advance
>
>
>
> claudio
>
> ****************************************************************
> ************
>
> *Whatsapp: +55 47 992451825 <%2B55%2047%2092451825>*
> https://claudiocesar.wordpress.com/ (my links HERE)
> https://github.com/claudiosa
> https://www.udemy.com/picat-uma-linguagem-de-programacao-multiparadigma/
> ****************************************************************
> *************
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> Beginners mailing list
> Beginners@haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
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