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[mkgmap-dev] patch for "part" filter

From Gerd Petermann GPetermann_muenchen at hotmail.com on Fri Apr 1 07:46:48 BST 2016

Hi Andrzej,

thanks for the patch. I agree about the null values, but I am not so sure
about the trailing separators, as it is documented (if my understanding is right)
I am waiting for feedback from the original authors
Franco Bez and Enrico Liboni, as I have no idea why they coded it like this.
Of course any other feedback is also welcomed.


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej at poczta.onet.pl>
Gesendet: Mittwoch, 30. März 2016 20:31
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: [mkgmap-dev] patch for "part" filter


I have tried to use substitution filter "part" and have found, that it
worked differently, than I expected. Some operation results in adding
trailing separator while others don't. Some filters return null, others
return "", which breaks evaluating formulas with "|".

I have attached a patch, that should change behavior of following filters:
"A1;A2;A3" "part:;<3"  -> old "A3;", patched "A3"
"A1;A2"    "part:;<3"  -> old null,  patched "A1;A2"
"A1"       "part:;>-2" -> old null,  patched "A1"
"A1;A2;A3" "part:;>3"  -> old "",    patched null
"A1;A2"    "part:;<-2" -> old "",    patched null

I have attached example data and style for testing the filter.

I'm not sure, what would be preferred result for following filters:
"A1"  "part:;<3"  -> result null or "A1"?
"A1"  "part:;>-3" -> result null or "A1"?

Both, current version and patched, return null. I think result "A1"
could be useful.

Best regards,

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