[REBOL] Parsing a "Brick Wall" - Need help!
From: webmaster::windsweptfarm::com at: 10-Sep-2002 10:53
Dear List,
Here's the background:
I have a stream of "NMEA sentences" coming from a GPS unit on a serial port.
I wish to parse the various elements within each sentence into variables/words.
The hickup in this is that Rebol wants to evaluate these elements and is convinced
that they are malformed data types. The $ prefix convinces Rebol that I am talking
money, while the decimals are also generating errors of their own.
How do I block this behaviour?
I want these elements to be vanilla values until they are shunted.
How can I insulate the data from evaluation prior to assignment?
This is a typical NMEA sentences of one type ($GPGLL) that I wish to package into variables:
$GPGLL,327.900,N,08056.851,W,141608,A*3E
Here is the code to pull only "$GPGLL" data from GPS unit on com1:
;START CODE==========>
GPS_STREAM: open/read/lines serial://port1/4800/8/none/1
while [0 <> (length? (NMEA_LINE: first GPS_STREAM))
][while [(GEO_POS: find/match NMEA_LINE "$GPGLL,")][
(print GEO_POS) BREAK ]]
close GPS_STREAM
;STOP CODE==========^
This prints all "NMEA sentences":
START CODE==========>
GPS_STREAM: open/read/lines serial://port1/4800/8/none/1
while [0 <> (length? (NMEA_LINE: first GPS_STREAM))][print NMEA_LINE]
close GPS_STREAM
;STOP CODE==========^
Here is a raw stream of NMEA sentences from the GPS unit via com port:
BTW: It is a simulation of the unit travelling at 160mph towards Garmin
(the gps manufacturer, in Kansas). That is why we see the word "GARMIN".
$GPRMC,143959,A,4309.445,N,08208.192,W,139.0,250.1,100902,008.1,W*78
$GPRMB,A,0.00,R,,GARMIN,3851.333,N,09447.941,W,629.5,250.0,139.0,V*2E
$GPGGA,143959,4309.443,N,08208.202,W,1,11,2.0,378.3,M,-35.0,M,,*7A
$GPGSA,A,3,03,09,14,15,17,18,21,23,26,29,31,,4.1,2.0,3.0*3D
$GPGSV,3,1,11,03,14,284,36,09,52,111,46,14,24,241,40,15,64,189,48*71
$GPGSV,3,2,11,17,52,167,46,18,75,357,49,21,46,302,45,23,24,094,40*73
$GPGSV,3,3,11,26,19,054,38,29,11,056,34,31,06,319,30,,,,*4C
$PGRME,15.0,M,22.5,M,15.0,M*1B
$GPGLL,4309.435,N,08208.231,W,143959,A*35
$PGRMZ,1241,f,3*2D
$PGRMM,WGS 84*06
$GPBOD,250.0,T,258.1,M,GARMIN,*50
$GPRTE,1,1,c,0,GARMIN*35
$GPWPL,3851.333,N,09447.941,W,GARMIN*49
$GPRMC,144001,A,4309.419,N,08208.291,W,139.0,250.1,100902,008.1,W*72
$GPRMB,A,0.00,R,,GARMIN,3851.333,N,09447.941,W,629.4,250.0,139.0,V*2F
$GPGGA,144001,4309.417,N,08208.301,W,1,11,2.0,378.3,M,-35.0,M,,*7A
$GPGSA,A,3,03,09,14,15,17,18,21,23,26,29,31,,4.1,2.0,3.0*3D
$GPGSV,3,1,11,03,14,284,36,09,52,111,46,14,24,241,40,15,64,189,48*71
$GPGSV,3,2,11,17,52,167,46,18,75,001,49,21,46,302,45,23,24,094,40*73
$GPGSV,3,3,11,26,19,054,38,29,11,056,34,31,06,319,30,,,,*4C
$PGRME,15.0,M,22.5,M,15.0,M*1B
$GPGLL,4309.409,N,08208.331,W,144001,A*38
$PGRMZ,1241,f,3*2D
$PGRMM,WGS 84*06
$GPBOD,250.0,T,258.1,M,GARMIN,*50
$GPRTE,1,1,c,0,GARMIN*35
$GPWPL,3851.333,N,09447.941,W,GARMIN*49
$GPRMC,144003,A,4309.393,N,08208.390,W,139.0,250.1,100902,008.1,W*75
$GPRMB,A,0.00,R,,GARMIN,3851.333,N,09447.941,W,629.4,250.0,139.0,V*2F
$GPGGA,144003,4309.390,N,08208.400,W,1,11,2.0,378.3,M,-35.0,M,,*76
$GPGSA,A,3,03,09,14,15,17,18,21,23,26,29,31,,4.1,2.0,3.0*3D
$GPGSV,3,1,11,03,14,284,36,09,52,111,46,14,24,241,40,15,64,189,48*71
$GPGSV,3,2,11,17,52,167,46,18,75,001,49,21,46,302,45,23,24,094,40*73
$GPGSV,3,3,11,26,19,054,38,29,11,056,34,31,06,319,30,,,,*4C
$PGRME,15.0,M,22.5,M,15.0,M*1B
$GPGLL,4309.382,N,08208.430,W,144003,A*38
$PGRMZ,1241,f,3*2D
$PGRMM,WGS 84*06
$GPBOD,250.0,T,258.1,M,GARMIN,*50
$GPRTE,1,1,c,0,GARMIN*35
$GPWPL,3851.333,N,09447.941,W,GARMIN*49
$GPRMC,144005,A,4309.366,N,08208.489,W,139.0,250.1,100902,008.1,W*76
$GPRMB,A,0.00,R,,GARMIN,3851.333,N,09447.941,W,629.3,250.0,139.0,V*28
$GPGGA,144005,4309.364,N,08208.499,W,1,11,2.0,378.3,M,-35.0,M,,*7B
$GPGSA,A,3,03,09,14,15,17,18,21,23,26,29,31,,4.1,2.0,3.0*3D
$GPGSV,3,1,11,03,14,284,36,09,52,111,46,14,24,241,40,15,64,189,48*71
$GPGSV,3,2,11,17,52,167,46,18,75,001,49,21,46,302,45,23,24,094,40*73
$GPGSV,3,3,11,26,19,054,38,29,11,056,34,31,06,319,30,,,,*4C
$PGRME,15.0,M,22.5,M,15.0,M*1B
$GPGLL,4309.356,N,08208.529,W,144005,A*3E
$PGRMZ,1241,f,3*2D
$PGRMM,WGS 84*06
$GPBOD,250.0,T,258.1,M,GARMIN,*50
$GPRTE,1,1,c,0,GARMIN*35
$GPWPL,3851.333,N,09447.941,W,GARMIN*49
$GPRMC,144007,A,4309.340,N,08208.589,W,139.0,250.1,100902,008.1,W*71
$GPRMB,A,0.00,R,,GARMIN,3851.333,N,09447.941,W,629.2,250.0,139.0,V*29
$GPGGA,144007,4309.337,N,08208.599,W,1,11,2.0,378.3,M,-35.0,M,,*7E
$GPGSA,A,3,03,09,14,15,17,18,21,23,26,29,31,,4.1,2.0,3.0*3D
$GPGSV,3,1,11,03,14,284,36,09,52,111,46,14,24,241,40,15,64,189,48*71
$GPGSV,3,2,11,17,52,167,46,18,75,001,49,21,46,302,45,23,24,094,40*73
$GPGSV,3,3,11,26,19,054,38,29,11,056,34,31,06,319,30,,,,*4C
$PGRME,15.0,M,22.5,M,15.0,M*1B
$GPGLL,4309.330,N,08208.628,W,144007,A*3E
$PGRMZ,1241,f,3*2D
$PGRMM,WGS 84*06
$GPBOD,250.0,T,258.1,M,GARMIN,*50
$GPRTE,1,1,c,0,GARMIN*35
$GPWPL,3851.333,N,09447.941,W,GARMIN*49
$GPRMC,144009,A,4309.314,N,08208.688,W,139.0,250.1,100902,008.1,W*7C
$GPRMB,A,0.00,R,,GARMIN,3851.333,N,09447.941,W,629.1,250.0,139.0,V*2A
$GPGGA,144009,4309.311,N,08208.698,W,1,11,2.0,378.3,M,-35.0,M,,*76
$GPGSA,A,3,03,09,14,15,17,18,21,23,26,29,31,,4.1,2.0,3.0*3D
$GPGSV,3,1,11,03,14,284,36,09,52,111,46,14,24,241,40,15,64,189,48*71
$GPGSV,3,2,11,17,52,167,46,18,75,001,49,21,46,302,45,23,24,094,40*73
Thanks in advance!
Jim
