Extract points from SpatialLines objects along with the corresponding Lines' ID

Thank you Fr?d?ric and Edzer for your replies.

Fr?d?ric, I didn't get your point but I am new to the sp library, it
will be clearer to me when I catch up.

The first solution provided by Edzer works great for me, and the
second one will quite likely be useful at some point.

Thanks again.

Best regards,

Bastien