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

Wed Feb 8 11:28:12 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

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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