Hi Andrzej, to be honest, I don't understand enough of the rule parsing to improve the syntax. I don't even know for sure why mkgmap:option:test!=true { add foo=bar} is not supported. Might be coding complexity, might be run time performance. On the other hand you already found the work around to use if (mkgmap:option:test=true) then else { add foo=bar} end I don't think that if-then can improve performance. The rules are not compiled in a way that would allow to skip something. On the other hand a lot of caching happens so that in rules like junction=roundabout & (highway=trunk | highway=trunk_link) [0x0c road_class=4 road_speed=2 resolution 24 continue] junction=roundabout & (highway=trunk | highway=trunk_link) [0x10801 resolution 18] the common expression is stored only once and the result of the first evaluation is simply reused in the 2nd rule. With the next rule junction=roundabout & (highway=primary | highway=primary_link) & mkgmap:fast_road=yes [0x0c road_class=4 road_speed=2 resolution 24 continue] the expression junction=roundabout is again reused and only the other expressions are computed. Only problem: When an action changes any tag of the object all cached results are cleared. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej@poczta.onet.pl> Gesendet: Montag, 30. Mai 2022 13:51 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] Some observations Hi Gerd, thanks for explanations.
the option --make-opposite-cycleways is implemented like this
Somehow I imagined, that opposite cycleway is magically added at a final step, when the main road is already prepared by style. Your way is more flexible, but needs more diligence in style. Actually I had to make a lot corrections in my style, when I realized how it works. It would be good to add your explanation to options.txt.
The manual has this note:
"There used to be some restrictions on the kind of expression you could use. Now the only restriction is you must have at least one test that depends on a tag existing. So you cannot match on everything, regardless of tags, or test for an object that does not have a tag." Sorry, I missed it. It is at the section, "Combining tag tests", while I was interested in a single test. I read the section "Allowed operations" and found no difference between using tag=value and tag!=value. This make me wonder, why "mkgmap:option:test=true" works but "mkgmap:option:test!=true" doesn't. To be true, I'm not understanding this explanation. What does it mean "tag existing"? Does tag "highway" exist but "mkgmap:synthesised" doesn't?
I wonder why mkgmap complains. Seems it checks only the "if" part.
I guess it is about "if then", most problems appear when I try to use this statement. Another question: is the condition of "if then" statement checked once or for each line included in the conditional block? I wonder whether "if then" could optimize processing of style. -- Best regards, Andrzej _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk https://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev