Demonstrating Sweep_line_2::get_subcurves 

Curves: 
10/1 1/1 20/1 1/1
10/1 -4/1 20/1 6/1
12/1 -4/1 12/1 3/1
20/1 6/1 20/1 1/1

Number of sub segments: 10

10/1 -4/1 -840/-70 140/-70
12/1 -4/1 -840/-70 140/-70
10/1 1/1 -840/-70 -70/-70
-840/-70 140/-70 -840/-70 -70/-70
-840/-70 -70/-70 12/1 3/1
-840/-70 -70/-70 -1500/-100 -100/-100
-840/-70 140/-70 -1500/-100 -100/-100
-1500/-100 -100/-100 20/1 1/1
-1500/-100 -100/-100 20/1 6/1
20/1 1/1 20/1 6/1