CGAL users discussion list

[Efi Fogel <>]

If the input does not comply with the precondition, that is, the input polygons are invalid according to the specification in the manual, the results are nondeterministic.
The program may halt and output wrong results or run forever, who cares, at least I don't. It's not worth it.
If I recall the original question, you can define a polygon-with-holes without an outer boundary and with several holes.
You can also obtain such a polygon-with-holes by providing the complement of the holes as input polygons to the complement Boolean operation.

On Mon, Nov 12, 2012 at 12:42 PM, Moore Rollo (THE ROYAL MARSDEN NHS FOUNDATION TRUST) <> wrote:

greetings all; Efi, is this in the manner of the halting problem?

 

the explanation being at a different level to the problem itself.

 

{regards; Rollo}

 

[deletia]

Or is it just that for "invalid" polygons the output is undefined, and
maybe sometimes right and sometimes wrong?

IMHO not checking for validity seems a good way to lead to pitfalls,
but I'm not an expert programmer so I'd appreciate an explanation as
to why things are the way they are.

Checking for validity, sometimes, is more expensive then running the procedure itself.
If we could check for validity, perhaps we could have also fix those invalid polygons....
 

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