[mkgmap-dev] To do: If-Then-Else

Wed Feb 8 12:32:18 GMT 2017

It would be easier for the parser without curly braces:
+1

I was gonna suggest not using curly-braces earlier but don't know enough
about parsers to make such a request. Seeing as they're already required in
other places, it would be advantageous to not require them again in this
context.

Dave

On Wed, Feb 8, 2017 at 6:28 PM, Steve Ratcliffe <steve at parabola.me.uk>
wrote:

>
> Hi
>
> don't know if this helps:
>> I see one possible implementation for a conditional rule like
>> if (<exp>) {
>>  some rules
>> } else {
>> other rules
>> }
>> where <exp> would be something like tag=val, maybe also a parameter given
>> to the program.
>> If someone knows how to implement the syntax parser for such an
>> if-thent-else clause the evaluation could simply
>>
>
> It would be easier for the parser without curly braces:
>
> if (<exp)
>  some rules
> else
>  other rules
> endif
>
> I could make that work.
>
> ..Steve
>
> translate the if (<exp>) to a rule like
>> exp {set special_var_x=true;}
>> and then add this special tag with tag=true or tag!=true to each
>> conditional rule.
>> So, we would not  need many changes in the evaluation of the rules, only
>> in the parser.
>>
>> Gerd
>>
>> ________________________________________
>> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von
>> Mike Baggaley <mike at tvage.co.uk>
>> Gesendet: Dienstag, 7. Februar 2017 18:22:32
>> An: mkgmap-dev at lists.mkgmap.org.uk
>> Betreff: Re: [mkgmap-dev] To do: If-Then-Else
>>
>> Hi Andrzej, can you not make use of mkgmap:country to handle this
>> scenario?
>>
>> mkgmap:country=DZA | mkgmap:country=AGO |  mkgmap:country=SHN |
>> mkgmap:country=BEN ... {set continent=AF}
>>
>> continent=AF & landuse=farmland [0x10f01 level 1]
>>
>> Would mkgmap be better with a mkgmap:continent variable using
>> place=continent added?
>>
>> Regards,
>> Mike
>>
>> -----Original Message-----
>> From: Andrzej Popowski [mailto:popej at poczta.onet.pl]
>> Sent: 07 February 2017 12:39
>> To: mkgmap-dev at lists.mkgmap.org.uk
>> Subject: Re: [mkgmap-dev] To do: If-Then-Else
>>
>> Hi Dave,
>>
>> I think the idea is to include some preprocessing capability to style
>> interpreter.
>>
>> I develop a single style for my topo maps, but I need some possibility
>> to get a small variation in style depending on region. For example I
>> prefer to show landuse=farmland on a map of Africa but to remove it on a
>> map of Europe. So instead of maintaining 2 nearly identical styles, I
>> would like to get a conditional statement, something like:
>>
>> if (SHOW_FARMS) (
>>         landuse=farmland [0x10f01 level 1]
>> )
>>
>> and then add (or not) an option to mkgmap like --style-define=SHOW_FARMS
>>
>> --
>> Best regards,
>> Andrzej
>>
>>
>> _______________________________________________
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>> mkgmap-dev at lists.mkgmap.org.uk
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>>
>>
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-- 
Dave Swarthout
Homer, Alaska
Chiang Mai, Thailand
Travel Blog at http://dswarthout.blogspot.com
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