Implement type system

src/grl-coordinates.adb

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+package body Grl.Coordinates is
+
+   function To_DD (DM_Base : Coordinate) return Coordinate is
+      DD_Target : Coordinate (DD);
+   begin
+
+      case DM_Base.Form is
+         when Relative => null;
+         when DD_Fine => null;
+         when DD => DD_Target := DM_Base;
+         when DDM =>
+            if DM_Base.DDM.Cardinal_Lat = North then
+               DD_Target.DD.Latitude :=
+                  DD_Meter_Scale_Lat (DM_Base.DDM.Degree_Lat)
+                  +
+                  DD_Meter_Scale_Lat (DM_Base.DDM.Minutes_Lat / 60.0);
+            end if;
+         when DMS => null;
+      end case;
+
+      return DD_Target;
+   end To_DD;
+
+end Grl.Coordinates;

src/grl-coordinates.ads

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+package Grl.Coordinates
+with SPARK_Mode => On
+is
+
+   --  ------------  --
+   --  Helper Units  --
+   --  ------------  --
+
+   --  DD Meter Scale
+   type DD_Meter_Scale_Lat is delta 1.0E-5 range -90.0 .. 90.0;
+   type DD_Meter_Scale_Lon is delta 1.0E-5 range -180.0 .. 180.0;
+
+   --  DD Centimeter Scale
+   type DD_Centimeter_Scale_Lat is delta 1.0E-7 range -90.0 .. 90.0;
+   type DD_Centimeter_Scale_Lon is delta 1.0E-7 range -180.0 .. 180.0;
+
+   --  DM Scale
+   type DM_Degree_Lat is range 0 .. 90;
+   type DM_Degree_Lon is range 0 .. 180;
+   --  1° = 60'; each Lat minute = 1.852km / 1 Naut Mile
+   type DM_Minutes is range 0 .. 60;
+   --  1° = 60'; each Lat minute = 1.852km / 1 Naut Mile
+   type DDM_Minutes is delta 1.0E-3 range 0.0 .. 60.000;
+   --  1' = 60''; 1° = 3600''; 1'' ~ 30.9m
+   type DM_Seconds is delta 1.0E-1 range 0.0 .. 60.0;
+
+   --  Cardinal directions
+   type Cardinal is (North, South, East, West);
+   type Ordinal is (North_East, South_East, South_West, North_West);
+
+   --  ------------------  --
+   --  Coordinate Formats  --
+   --  ------------------  --
+
+   --  Meter precision DD coordinates
+   type Format_DD is record
+		Latitude       : DD_Meter_Scale_Lat;
+      Longitude      : DD_Meter_Scale_Lon;
+	end record;
+
+   --  Centimeter precision DD coordinates
+   type Format_DD_Fine is record
+		Latitude       : DD_Centimeter_Scale_Lat;
+      Longitude      : DD_Centimeter_Scale_Lon;
+	end record;
+
+   --  DMS
+   type Format_DMS is record
+		Degree_Lat     : DM_Degree_Lat;
+      Degree_Lon     : DM_Degree_Lon;
+      Minutes_Lat    : DM_Minutes;
+      Minutes_Lon    : DM_Minutes;
+      Seconds_Lat    : DM_Seconds;
+      Seconds_Lon    : DM_Seconds;
+      Cardinal_Lat   : Cardinal;
+      Cardinal_Lon   : Cardinal;
+	end record
+   with Dynamic_Predicate =>
+      Format_DMS.Cardinal_Lat in North | South
+      and then
+      Format_DMS.Cardinal_Lon in East | West;
+
+   --  DDM
+   type Format_DDM is record
+		Degree_Lat : DM_Degree_Lat;
+      Degree_Lon : DM_Degree_Lon;
+      Minutes_Lat : DDM_Minutes;
+      Minutes_Lon : DDM_Minutes;
+      Cardinal_Lat : Cardinal;
+      Cardinal_Lon : Cardinal;
+	end record
+   with Dynamic_Predicate =>
+      Format_DDM.Cardinal_Lat in North | South
+      and then
+      Format_DDM.Cardinal_Lon in East | West;
+
+   --  --------------------------  --
+   --  Coordinate Type Definition  --
+   --  --------------------------  --
+
+   type Format is (Relative, DD, DD_Fine, DMS, DDM);
+   type Coordinate (Form : Format := Relative) is record
+		case Form is
+         when Relative =>
+            null;
+         when DD =>
+            DD : Format_DD;
+         when DD_Fine =>
+            DD_Fine : Format_DD_Fine;
+         when DMS =>
+            DMS : Format_DMS;
+         when DDM =>
+            DDM : Format_DDM;
+      end case;
+	end record;
+
+   --  ----------------------------  --
+   --  Converter / helper functions  --
+   --  ----------------------------  --
+
+   --  Converter with DD target
+   --  @name      To_DD
+   --  @return    Coordinate
+ 	--  @parameter DM_Base  :  Coordinate
+	--  @description Take any coordinate and return a DD formatted coordinate.
+   function To_DD (DM_Base : Coordinate) return Coordinate
+      with Pre =>
+         (DM_Base.Form = DD) or else
+         (DM_Base.Form = DMS) or else
+         (DM_Base.Form = DDM);
+
+end Grl.Coordinates;