Add global-positioning-system exercise (#444)

config.json

@@ -893,6 +893,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 1
+      },
+      {
+        "slug": "global-positioning-system",
+        "name": "Global Positioning System",
+        "uuid": "14d2d6a7-6d6c-4cdf-b0cb-8df1093e8f70",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 1
       }
     ],
     "foregone": [

exercises/practice/global-positioning-system/.docs/hints.md

@@ -0,0 +1,45 @@
+# Hints
+
+## General
+
+- [Wikipedia's Definite Clause Grammar page](https://en.wikipedia.org/wiki/Definite_clause_grammar) gives a great overview of DCGs
+- The [Prolog DCG Primer](https://www.metalevel.at/prolog/dcg) has a very useful introduction to Prolog DCGs
+- The [SWIPL dcg/basics docs](https://www.swi-prolog.org/pldoc/doc/_SWI_/library/dcg/basics.pl) lists the built-in primitives you can use
+
+## 3. Support all whitespace (except newlines)
+
+- There is a [built-in primitive](https://www.swi-prolog.org/pldoc/doc/_SWI_/library/dcg/basics.pl) you can use for this
+
+## 4. Parse the latitude's hemisphere
+
+- DCG rules can have variables like regular facts or rules
+- DCG rules can have multiple declarations like regular facts or rules
+
+## 5. Parse the longitude's hemisphere
+
+- DCG rules can have variables like regular facts or rules
+- DCG rules can have multiple declarations like regular facts or rules
+
+## 6. Parse degrees
+
+- There is a [built-in primitive](https://www.swi-prolog.org/pldoc/doc/_SWI_/library/dcg/basics.pl) you can use for this
+
+## 7. Parse latitude degrees
+
+- You can re-use the `degrees` rule
+- The `{}//1` language construct can be used to invoke Prolog predicates from within a rule
+
+## 9. Parse latitude
+
+- The format for a latitude is: `<LATITUDE_DEGREES> <LATITUDE_HEMISPHERE>`
+- Re-use the rules you've already implemented
+
+## 10. Parse longitude
+
+- The format for a longitude is: `<LONGITUDE_DEGREES> <LONGITUDE_HEMISPHERE>`
+- Re-use the rules you've already implemented
+
+## 11. Parse coordinate
+
+- The format for a coordinate is: `<LATITUDE_DEGREES> <LATITUDE_HEMISPHERE>, <LONGITUDE_DEGREES> <LONGITUDE_HEMISPHERE>`
+- Re-use the rules you've already implemented

exercises/practice/global-positioning-system/.docs/instructions.md

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+# 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
+<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](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.
+```

exercises/practice/global-positioning-system/.docs/introduction.md

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+# Introduction
+
+You're a huge fan of [geocaching](https://en.wikipedia.org/wiki/Geocaching), which combines your love for the outdoors with a love for solving puzzles.
+Whilst the local geocaching website lists the GPS coordinates of all caches, it does _not_ support creating an efficient route for gathering them.
+It so happens you have pathfinding software installed on your machine, but it uses a different GPS format from the geocaching website.
+To feed the data into the pathfinding software, you'll need to parse the degrees and hemisphere for both the latitude and longitude of each GPS coordinate on the website.

exercises/practice/global-positioning-system/.meta/config.json

@@ -0,0 +1,17 @@
+{
+  "authors": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "global_positioning_system.pl"
+    ],
+    "test": [
+      "global_positioning_system_tests.plt"
+    ],
+    "example": [
+      ".meta/global_positioning_system.example.pl"
+    ]
+  },
+  "blurb": "Parse GPS coordinates into their individual components"
+}

exercises/practice/global-positioning-system/.meta/global_positioning_system.example.pl

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+:- use_module(library(dcg/basics)).
+
+comma --> ",".
+space --> white.
+
+latitude_hemisphere(north) --> "N".
+latitude_hemisphere(south) --> "S".
+
+longitude_hemisphere(east) --> "E".
+longitude_hemisphere(west) --> "W".
+
+degrees(Degrees) --> float(Degrees).
+latitude_degrees(Degrees) --> degrees(Degrees), { Degrees >= 0, Degrees =< 90 }.
+longitude_degrees(Degrees) --> degrees(Degrees), { Degrees >= 0, Degrees =< 180 }.
+
+latitude(Degrees, Hemisphere) --> latitude_degrees(Degrees), space, latitude_hemisphere(Hemisphere).
+longitude(Degrees, Hemisphere) --> longitude_degrees(Degrees), space, longitude_hemisphere(Hemisphere).
+
+coordinate(Latitude, LatitudeHemisphere, Longitude, LongitudeHemisphere) -->
+    latitude(Latitude, LatitudeHemisphere), comma, space, longitude(Longitude, LongitudeHemisphere).

exercises/practice/global-positioning-system/global_positioning_system.pl

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+:- use_module(library(dcg/basics)).
+
+comma.
+space.
+
+latitude_hemisphere(Hemisphere).
+longitude_hemisphere(Hemisphere).
+
+degrees(Degrees).
+latitude_degrees(Degrees).
+longitude_degrees(Degrees).
+
+latitude(Degrees, Hemisphere).
+longitude(Degrees, Hemisphere).
+
+coordinate(Latitude, LatitudeHemisphere, Longitude, LongitudeHemisphere).