## Kernel::IsHorizontal_2

A model for this must provide:

bool | fo.operator() ( Kernel::Line_2 o)
|  | returns true iff o is horizontal.
bool | fo.operator() ( Kernel::Ray_2 o)
|  | returns true iff o is horizontal.
bool | fo.operator() ( Kernel::Segment_2 o)
|  | returns true iff o is horizontal.

### Refines

AdapatableFunctor (with one argument)

### See Also

CGAL::Line_2<Kernel>
CGAL::Ray_2<Kernel>
CGAL::Segment_2<Kernel>