Re: [Boost-users] Boost-users Digest, Vol 2769, Issue 5

Subject: Re: [Boost-users] Boost-users Digest, Vol 2769, Issue 5
From: Tom Tan (ttan_at_[hidden])
Date: 2011-07-01 00:03:56

------------------------------
> 
> Date: Thu, 30 Jun 2011 15:00:13 -0400 (EDT)
> From: Jeremiah Willcock <jewillco_at_[hidden]>
> To: boost-users_at_[hidden]
> Subject: Re: [Boost-users] [Graph]questions regarding
> 	boost::graph::adjacency_list constructor prototype
> 
> On Thu, 30 Jun 2011, Tan, Tom (Shanghai) wrote:
> 
> > 
> > While studying boost.graph, I stumbled upon this constructor
definition:
> > 
> > ????template <class EdgeIterator>
> > 
> > ??? adjacency_list(EdgeIterator first, EdgeIterator last,
> > 
> > ????????????????????????? vertices_size_type n,
> > 
> > ????????????????????????? edges_size_type = 0,
> > 
> > ????????????????????????? const GraphProperty& p = GraphProperty())
> > 
> > ????? : 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.

Nice to know this trick. Never knew that the 'x' can be omitted in this
case.

> 
> > 
> > -????????? 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.

I guessed so but it's better to confirmed.

Thanks for the help.

-Tom