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

Tue Feb 7 17:40:47 GMT 2017

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
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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