Re: [Boost-users] [Graph]questions regarding boost::graph::adjacency_list constructor prototype

Subject: Re: [Boost-users] [Graph]questions regarding boost::graph::adjacency_list constructor prototype
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2011-06-30 15:00:13

On Thu, 30 Jun 2011, Tan, Tom (Shanghai) wrote:

> 
> While studying boost.graph, I stumbled upon this constructor definition:
> 
> Â Â Â Â template <class EdgeIterator>
> 
> Â Â Â  adjacency_list(EdgeIterator first, EdgeIterator last,
> 
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  vertices_size_type n,
> 
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  edges_size_type = 0,
> 
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  const GraphProperty& p = GraphProperty())
> 
> Â Â Â Â Â  : Base(n, first, last), m_property(new graph_property_type(p))
> 
> { }
> 
> I have 2 questions here:
> 
> -          What does “edges_size_type = 0,” means here?  Assigning a value to a TYPE, instead of a parameter? Can
> anyone please point me to an explanation of this grammar usage?

It's like if the code was "edges_size_type x = 0", but since the parameter 
is not used, removing the name avoids compiler warnings.

> 
> -          Why the necessary of edges_size_type = 0 parameter,  since there’s a range pair of “EdgeIterator first,
> EdgeIterator last”?

It is not necessary, since the value of that parameter is never used.  It 
is probably there match the interface of some other constructor, either in 
adjacency_list or some other graph class.

-- Jeremiah Willcock