Hi Dave,
it is just an example for this case
if (a=b) then
c=d {delete a}
e=f {do something}
end
I don't say that my example is useful.
Gerd
________________________________________
Von: mkgmap-dev <[email protected]> im Auftrag von Dave
Swarthout <[email protected]>
Gesendet: Montag, 27. Februar 2017 12:04:33
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev] if-then in style
Hi Gert,
In your example you use proposed=footway. I've never seen any tagging like that
- what does it mean? Give us a better description of what you're trying to
accomplish in your test statement
if (highway=proposed)
proposed=footway {delete highway}
surface=asphalt {echotags "test" } [... ]
end
On Mon, Feb 27, 2017 at 5:51 PM, Gerd Petermann
<[email protected]<mailto:[email protected]>> wrote:
Hi all,
I try to make up my mind about what is needed and what is not.
1) I did not yet find a good reason to have an else clause, so I think we
should start without implementing it
unless one can give a good example.
2) The banch now implements the syntax
if (EXPR) then
...
end
by adding the expression EXPR to each of the rules between 'then' and 'end' .
Nested if-then are allowed.
This might cause confusion in the following case:
if (highway=proposed)
proposed=footway {delete highway}
surface=asphalt {echotags "test" } [... ]
end
What should happen for a way with highway=proposed, proposed=footway,
surface=asphalt ?
I'd expect that the 2nd rule with echotags is triggered, but it is not because
after the interpretation of the if-then clause the rules look like this:
proposed=footway & highway=proposed {delete highway}
surface=asphalt & highway=proposed {echotags "test" } [... ]
and since the first rule deletes the highway tag the 2nd isn't triggered.
My suggested interpretation was like this:
highway=proposed {set mkgmap:if:1000=true}
proposed=footway & mkgmap:if:1000=true {delete highway}
surface=asphalt & mkgmap:if:1000=true {echotags "test" } [... ]
And I think that we should make sure that those generated special tags like
mkgmap:if:1000 are not used directly by the style author .
Another option might be to disallow the modification of any tag which appears
in EXPR.
No idea if that would be easier to implement but I fear that it would lead to
very confusing error messages.
Comments?
ciao,
Gerd
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Dave Swarthout
Homer, Alaska
Chiang Mai, Thailand
Travel Blog at http://dswarthout.blogspot.com
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