[igraph] how to "collapse" a network

[Wet Bell Diver]

Dear list,

I have the following two straightforward issues. I Have a dataset of 
connections between companies (-having a deal together).
The edglist would look something like:
'COMP 1' -- 'COMP 2'
'COMP 1' -- 'COMP 3'
'COMP 2' -- 'COMP 4'
'COMP 1' -- 'COMP 3'
'COMP 5' -- 'COMP 6'
'COMP 1' -- 'COMP 3'
'COMP 1' -- 'COMP 2'
et cetera, for a few thousand vertices (between 800 and 2500, depending 
on the continent)

It happens frequently that the same companies engage in multiple deals 
together, but each deal is represented by a line in my data. As a 
result, you see that 'COMP 1' -- 'COMP 2' occurs twice.
I would like to be able to collapse this to a weighted edge list where 
'COMP 1' -- 'COMP 2' occurs only once but with value 2, 'COMP 1' -- 
'COMP 3' occurs only once having value 3, et cetera.
There must be a very simple way of doing this, but how?

Second, each company has several attributes, including industry. One of 
the things I would like to do is to collapse the entire
company*company network into a weigted industry*industry network. This 
would reduce the network from approx. 2000*2000 to 40*40.
How can I construct such a weighted network in igraph?

thank you,
Peter Verbeet