Its usage is quite simple, for example, you can count the number of rows in an LP lp: 
int count=0; for (LpBase::RowIt c(lp); c!=INVALID; ++c) ++count;
#include <lemon/lp_base.h>
 Inheritance diagram for LpBase::RowIt:Public Member Functions | |
| RowIt () | |
| Default constructor.   | |
| RowIt (const LpBase &solver) | |
| RowIt (const Invalid &) | |
| Invalid constructor & conversion.   | |
| RowIt & | operator++ () | 
| Next row.   | |
| RowIt | ( | ) |  [inline] | 
        
Initialize the iterator to be invalid.
| RowIt& operator++ | ( | ) |  [inline] | 
        
Assign the iterator to the next row.
 1.7.3