Made lots and lots of modification...
Dinner time commit.
Cleaned up a bit
Experimenting with make file.
Added test files for each class
Resolved a dangerous but subtle bug in gpf_vector::resize() function.
Working with opeartor overload.
added the const specifier to all the appropriate members.
Operator overloading of simple_matrix, direted_graph and gpf_vector almost
done.
Ipmroved the << operator of directed_graph class.
Also added the >> operator for graph input from terminal.
and lots other.....
Prettifyied the graph output a bit.
Fixed a bug in >>directed_graph function.