I am having a bit of trouble determining the exact meaning of this line here:
TinyGPS &operator << (char c) {encode(c); return *this;}
It is of course part of the library TinyGPS which I am using to parse an NMEA string from my EM-406A GPS Sensor. I am taking apart the library right now so I can determine the cause of a locking issue with the sensor. I came across this and although I have a good understandings of the basics of C++ I am confused by this. Does anyone know what exactly is happening with this line. I am pasting the context of the whole code below which comes from TinyGPS.h. The rest of it looks pretty straightforward to me so far.
/*
TinyGPS - a small GPS library for Arduino providing basic NMEA parsing
Based on work by and "distance_to" and "course_to" courtesy of Maarten Lamers.
Suggestion to add satellites(), course_to(), and cardinal(), by Matt Monson.
Copyright (C) 2008-2012 Mikal Hart
All rights reserved.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef TinyGPS_h
#define TinyGPS_h
#if defined(ARDUINO) && ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif
#define _GPS_VERSION 12 // software version of this library
#define _GPS_MPH_PER_KNOT 1.15077945
#define _GPS_MPS_PER_KNOT 0.51444444
#define _GPS_KMPH_PER_KNOT 1.852
#define _GPS_MILES_PER_METER 0.00062137112
#define _GPS_KM_PER_METER 0.001
// #define _GPS_NO_STATS
class TinyGPS
{
public:
enum {
GPS_INVALID_AGE = 0xFFFFFFFF, GPS_INVALID_ANGLE = 999999999,
GPS_INVALID_ALTITUDE = 999999999, GPS_INVALID_DATE = 0,
GPS_INVALID_TIME = 0xFFFFFFFF, GPS_INVALID_SPEED = 999999999,
GPS_INVALID_FIX_TIME = 0xFFFFFFFF, GPS_INVALID_SATELLITES = 0xFF,
GPS_INVALID_HDOP = 0xFFFFFFFF
};
static const float GPS_INVALID_F_ANGLE, GPS_INVALID_F_ALTITUDE, GPS_INVALID_F_SPEED;
TinyGPS();
bool encode(char c); // process one character received from GPS
TinyGPS &operator << (char c) {encode(c); return *this;}
// lat/long in hundred thousandths of a degree and age of fix in milliseconds
void get_position(long *latitude, long *longitude, unsigned long *fix_age = 0);
// date as ddmmyy, time as hhmmsscc, and age in milliseconds
void get_datetime(unsigned long *date, unsigned long *time, unsigned long *age = 0);
// signed altitude in centimeters (from GPGGA sentence)
inline long altitude() { return _altitude; }
// course in last full GPRMC sentence in 100th of a degree
inline unsigned long course() { return _course; }
// speed in last full GPRMC sentence in 100ths of a knot
inline unsigned long speed() { return _speed; }
// satellites used in last full GPGGA sentence
inline unsigned short satellites() { return _numsats; }
// horizontal dilution of precision in 100ths
inline unsigned long hdop() { return _hdop; }
void f_get_position(float *latitude, float *longitude, unsigned long *fix_age = 0);
void crack_datetime(int *year, byte *month, byte *day,
byte *hour, byte *minute, byte *second, byte *hundredths = 0, unsigned long *fix_age = 0);
float f_altitude();
float f_course();
float f_speed_knots();
float f_speed_mph();
float f_speed_mps();
float f_speed_kmph();
static int library_version() { return _GPS_VERSION; }
static float distance_between (float lat1, float long1, float lat2, float long2);
static float course_to (float lat1, float long1, float lat2, float long2);
static const char *cardinal(float course);
#ifndef _GPS_NO_STATS
void stats(unsigned long *chars, unsigned short *good_sentences, unsigned short *failed_cs);
#endif
private:
enum {_GPS_SENTENCE_GPGGA, _GPS_SENTENCE_GPRMC, _GPS_SENTENCE_OTHER};
// properties
unsigned long _time, _new_time;
unsigned long _date, _new_date;
long _latitude, _new_latitude;
long _longitude, _new_longitude;
long _altitude, _new_altitude;
unsigned long _speed, _new_speed;
unsigned long _course, _new_course;
unsigned long _hdop, _new_hdop;
unsigned short _numsats, _new_numsats;
unsigned long _last_time_fix, _new_time_fix;
unsigned long _last_position_fix, _new_position_fix;
// parsing state variables
byte _parity;
bool _is_checksum_term;
char _term[15];
byte _sentence_type;
byte _term_number;
byte _term_offset;
bool _gps_data_good;
#ifndef _GPS_NO_STATS
// statistics
unsigned long _encoded_characters;
unsigned short _good_sentences;
unsigned short _failed_checksum;
unsigned short _passed_checksum;
#endif
// internal utilities
int from_hex(char a);
unsigned long parse_decimal();
unsigned long parse_degrees();
bool term_complete();
bool gpsisdigit(char c) { return c >= '0' && c <= '9'; }
long gpsatol(const char *str);
int gpsstrcmp(const char *str1, const char *str2);
};
#if !defined(ARDUINO)
// Arduino 0012 workaround
#undef int
#undef char
#undef long
#undef byte
#undef float
#undef abs
#undef round
#endif
#endif
Thank is advance...
Kind Regards.