Use:
- perfect forwarding in objects of the kernel (`Point_2`, `Point_3`,
`Vector_2`, `Vector_3`), and also in `PointC2`, and `PointC3`
(that forward to the equivalent vector)
- constructors with rvalue references in `VectorC2` and `VectorC3`.
The difficulty is to detect/define which constructions are "trivial"
and must not be wrapped into `Converting_construction`. Otherwise the
use of `Cartesian_converter`, that uses trivial constructions itself,
can lead to loops and infinite call stacks.
Instead of having the return type wrapped in a `Needs_FT` tag,
not the call operator overloads that can be called with `RT` are
"tagged" by adding a last argument of type `RT_sufficient` with a
default value.
This commit introduces a new kind of predicate in
`<CGAL/Kernel/interface_macros.h>`. In addition to
- `CGAL_kernel_pred` for predicates,
- `CGAL_Kernel_pred_RT` for predicates that can be implemented using a
ring-type,
now there is also:
- `CGAL_Kernel_pred_RT_or_FT` for predicates with multiple overloads of
`operator()`, some needing a field type and other needing a ring type
(without the division operator).
The C++ code can discriminate between the two cases with a special wrapper
for the return type: `CGAL::Needs_FT<result_type` instead of `result_type`
(defined in `<CGAL/tags.h>`.
In `<CGAL/Filtered_predicate.h>`, in addition to the usual class template
`Filtered_predicate`, there is now also `Filtered_predicate_RT_FT` that
takes three predicates as template parameters instead of two:
- the exact predicate with an ring-type,
- the exact predicate with a field-type,
- the approximate predicate (with `Interval_nt` as number-type).
For the moment, only `Compare_distance_3` in
`<CGAL/Cartesian/function_objects.h>` is using the new
`Filtered_predicate_RT_FT`.
Before this commit, the file
`Kernel_23/test/Kernel_23/include/CGAL/_test_new_3.h` was testing
`Compare_distance_3` only with three points or for points. This commit adds:
- a test with `Point_3, Point_3, Segment_3`, and
- a test with `Line_3, Point_3, Point_3`, that actually needs a field type
with its current implementation.
In the test `Kernel_23/test/Kernel_23/Filtered_cartesian.cpp`, the macro
`CGAL_NO_MPZF_DIVISION_OPERATOR` is defined, to remove the division operator
from `CGAL::Mpzf`. `CGAL::Mpzf` is a ring-type, even with its `operator/`
(because that `operator/` can only compute exact divisions), but with
`CGAL_NO_MPZF_DIVISION_OPERATOR` defined, that is now checked by the compiler.