RE: C++ parser library for NMEA GPS data - pt. 4: We have C++ objects and containers: So what?

shabaz — Sat, 10 Aug 2024 21:52:33 GMT

Hi Jan,

The debugger is STL aware? Very neat. I had expected it not to be capable of revealing the contents of the container at all!

RE: C++ parser library for NMEA GPS data - pt. 4: We have C++ objects and containers: So what?

Jan Cumps — Sat, 10 Aug 2024 13:20:15 GMT

to get all valid satellites out of one gsv object (can be between 1 and 4):

o: gsv object
o.sats: container of sat objects

    auto sts = o.sats | std::views::filter([](const nmea::gsv_sat& s){ return s.prn != 0;});

prn is the satellite's "id".

possible code:

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:a17079ed-0610-4b5b-917a-9881a20259dd:type=c_cpp&text=void%20list_satellites%28const%20nmea%3A%3Agsv%26%20o%29%20%7B%0D%0A%20%20%20%20auto%20sts%20%3D%20o.sats%20%7C%20std%3A%3Aviews%3A%3Afilter%28%5B%5D%28const%20nmea%3A%3Agsv_sat%26%20s%29%7B%20return%20s.prn%20%21%3D%200%3B%7D%29%3B%0D%0A%20%20%20%20print_talker%28o.source%29%3B%0D%0A%20%20%20%20printf%28%22%20sat%20id%3A%20%22%29%3B%0D%0A%20%20%20%20for%20%28const%20auto%26%20s%20%3A%20sts%29%20%7B%0D%0A%20%20%20%20%20%20printf%28%22%20%25i%22%2C%20s.prn%29%3B%0D%0A%20%20%20%20%7D%0D%0A%20%20%20%20printf%28%22.%20%5Cr%5Cn%22%29%3B%0D%0A%20%20%20%20return%3B%0D%0A%7D%0D%0A]

looping over all our gsv objects to get their satellites:

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:bc476ac0-a3be-43c7-a20a-0dcb58c44b15:type=c_cpp&text=%20%20%20%20%20%20%20%20for%28const%20auto%26%20g%20%3A%20std%3A%3Aranges%3A%3Asubrange%28gsv_set.begin%28%29%2C%20gsv_set.begin%28%29%20%2B%20count%29%20%29%20%7B%0D%0A%20%20%20%20%20%20%20%20%20%20%20%20list_satellites%28g%29%3B%0D%0A%20%20%20%20%20%20%20%20%7D%0D%0A]

result:

gps count: 4
glonass count: 3
gps sat id: 9 6 4 11. 
gps sat id: 7 3 20 19. 
gps sat id: 26 31 30 49. 
gps sat id: 36. 
glonass sat id: 71 86 87 70. 
glonass sat id: 80 72 73 79. 
glonass sat id: 85 85.

The last gps object has 1 satellite. The last glonass gsv object had 2. You can see that the std::views::filter (as defined in the predicate s.prn != 0) nicely does not include the full array of 4 possible satellites. But only the ones that match the filter.

Again, done without writing a custom filter, but using a STL construct.