Global Positioning System

Instructions

Your task is to parse GPS coordinates. Each coordinate is formatted using the Decimal Degrees format variant with explicit hemispheres:

<LATITUDE_DEGREES> <LATITUDE_HEMISPHERE>, <LONGITUDE_DEGREES> <LONGITUDE_HEMISPHERE>

These are the allowed values for each individual component:

• <LATITUDE_DEGREES>: a floating-point number in the range 0..90 (inclusive)
• <LATITUDE_HEMISPHERE>: either N or S
• <LONGITUDE_DEGREES>: a floating-point number in the range 0..180 (inclusive)
• <LONGITUDE_HEMISPHERE>: either E or W

For example, "48.8584 N, 2.2945 E" parses into:

• <LATITUDE_DEGREES>: 48.8584
• <LATITUDE_HEMISPHERE>: N
• <LONGITUDE_DEGREES>: 2.2945
• <LONGITUDE_HEMISPHERE>: E

You have 11 tasks, in which you'll incrementally parse GPS coordinates. You'll be using Prolog's Definite Clause Grammar (DCG) support, which are designed to parse structured text.

:- use_module(library(dcg/basics)).

1. Parse a comma

Implement the comma rule to parse a single comma (","):

?- string_codes(",", Codes), phrase(comma, Codes).

2. Parse a space

Implement the space rule to parse a single space (" "):

?- string_codes(" ", Codes), phrase(space, Codes).

3. Support all whitespace (except newlines)

Modify the space rule to parse all whitespace, except for newlines:

?- string_codes("\t", Codes), phrase(space, Codes).

?- string_codes("\n", Codes), phrase(space, Codes).
false.

4. Parse the latitude's hemisphere

The hemisphere of the latitude can be either "N" or "S", which should be parsed to the north or south atom. Implement the latitude_hemisphere rule to parse the latitude's hemisphere:

?- string_codes("N", Codes), phrase(latitude_hemisphere(Hemisphere), Codes).
Hemisphere = north.

5. Parse the longitude's hemisphere

The hemisphere of the longitude can be either "E" or "W", which should be parsed to the east or west atom. Implement the longitude_hemisphere rule to parse the longitude's hemisphere:

?- string_codes("E", Codes), phrase(longitude_hemisphere(Hemisphere), Codes).
Hemisphere = east.

6. Parse degrees

The degrees of a longitude or latitude ire defined as a floating-point number. Implement the degrees rule to parse floating-point numbers:

?- string_codes("748.012", Codes), phrase(degrees(Degrees), Codes).
Degrees = 748.012.

7. Parse latitude degrees

Latitude degrees are not just floating-point numbers, but floating-point numbers in the range 0..90 (inclusive). Implement the latitude_degrees rule to parse latitude degrees using the above range:

?- string_codes("48.745", Codes), phrase(latitude_degrees(Degrees), Codes).
Degrees = 48.745.

?- string_codes("117.844", Codes), phrase(latitude_degrees(Degrees), Codes).
false.

8. Parse longitude degrees

Longitude degrees are not just floating-point numbers, but floating-point numbers in the range 0..180 (inclusive). Implement the longitude_degrees rule to parse longitude degrees using the above range:

?- string_codes("178.773", Codes), phrase(longitude_degrees(Degrees), Codes).
Degrees = 178.773.

?- string_codes("-22.523", Codes), phrase(longitude_degrees(Degrees), Codes).
false.

9. Parse latitude

Latitudes have two parts: their degrees and hemisphere, which are separated by a space. Implement the latitude rule to parse a latitude:

?- string_codes("56.101 N", Codes), phrase(latitude(Degrees, Hemisphere), Codes).
Degrees = 56.101,
Hemisphere = north.

10. Parse longitude

Latitudes have two parts: their degrees and hemisphere, which are separated by a space. Implement the latitude rule to parse a latitude:

?- string_codes("143.889 W", Codes), phrase(longitude(Degrees, Hemisphere), Codes).
Degrees = 143.889,
Hemisphere = west.

11. Parse coordinate

Coordinates have two parts: their latitude and longitude, which are separated by a comma followed by a space. Implement the coordinate rule to parse both the latitude (degrees and hemisphere):

?- string_codes("48.8584 N, 2.2945 E", Codes), phrase(coordinate(Latitude, LatitudeHemisphere, Longitude, LongitudeHemisphere), Codes).
Latitude = 48.8584,
LatitudeHemisphere = north,
Longitude = 2.2945,
LongitudeHemisphere = east.