# Instructions Your task is to parse GPS coordinates. Each coordinate is formatted using the [Decimal Degrees format](https://en.wikipedia.org/wiki/Decimal_degrees) variant with explicit hemispheres: ```text , ``` These are the allowed values for each individual component: - ``: a floating-point number in the range 0..90 (inclusive) - ``: either `N` or `S` - ``: a floating-point number in the range 0..180 (inclusive) - ``: either `E` or `W` For example, `"48.8584 N, 2.2945 E"` parses into: - ``: 48.8584 - ``: N - ``: 2.2945 - ``: E You have 11 tasks, in which you'll incrementally parse GPS coordinates. You'll be using Prolog's [Definite Clause Grammar](https://en.wikipedia.org/wiki/Definite_clause_grammar) (DCG) support, which are designed to parse structured text. ````exercism/note To help you get started, the stub file already includes the [`dcg/basics` library](https://www.swi-prolog.org/pldoc/doc/_SWI_/library/dcg/basics.pl) via: ```prolog :- use_module(library(dcg/basics)). ``` ```` ## 1. Parse a comma Implement the `comma` rule to parse a single comma (`","`): ```prolog ?- string_codes(",", Codes), phrase(comma, Codes). ``` ## 2. Parse a space Implement the `space` rule to parse a single space (`" "`): ```prolog ?- string_codes(" ", Codes), phrase(space, Codes). ``` ## 3. Support all whitespace (except newlines) Modify the `space` rule to parse _all_ whitespace, except for newlines: ```prolog ?- 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: ```prolog ?- 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: ```prolog ?- 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: ```prolog ?- 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: ```prolog ?- 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: ```prolog ?- 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: ```prolog ?- 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: ```prolog ?- 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): ```prolog ?- 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. ```