[mkgmap-dev] Work on is_in branch

Tue Feb 18 07:13:00 GMT 2020

Hi Gerd

The two most common cases that I imagine users will want to match are
lines inside the polygon(s) and lines outside.

Inside lines will frequently meet the edge, and I don't think these
should fail the inside test.

Outside lines will, less frequently, meet the edge, and I don't think
these should fail the outside test.

Often there will be 2 lines, joining at edge of the polygon, that make
a continuous highway that is the entrance to the polygon. Both of these
will have an ON component.

So, the flag test for inside lines should be "hasIn && !hasOut" and for
outside lines should be "hasOut && !hasIn".

Expressing the outside test as the negative, in keeping with the
is_in() methods expressing in-ness, it becomes "hasIn || !hasOut".
I had expressed this as "hasIn || !(hasIn || hasOut)", because "!(hasIn
|| hasOut)" is all_ON, and this matches the method being called,
ambiguously, ANY_IN_OR_ON (ON_OR_ANY_IN would have been better) but
they are logically equivalent.

This expressing as in-ness seems to be the cause of these problems we
are discussing and maybe now is the time to abandon it.

I suggest replacing ANY_IN_OR_ON with SOME_OUT_NONE_IN, giving it the
method string "none", like SOME_IN_NONE_OUT is referenced as "all".

Ticker

On Mon, 2020-02-17 at 19:16 +0000, Gerd Petermann wrote:
> Hi Ticker,
> 
> I would except
>  +any_in_or_on+ - if is_in(...,any_in_or_on)=false, all is outside,
> none is in or on the edge.
> 
> Or name it
> +all_out+ - if is_in(...,all_out)=true, all is outside, none is in or
> on the edge.
> 
> A method that returns true when all is either out or on the edge
> could be called
> +out-or-on+
> 
> Gerd