Add initial prototype.

3-mid/physics/interface/source/physics-joint-hinge.ads

@@ -0,0 +1,23 @@
+package physics.Joint.hinge
+--
+-- An interface to a hinge joint.
+--
+is
+   type Item is  limited interface
+             and Joint.item;
+
+   type View is access all Item'Class;
+
+
+
+   procedure Limits_are  (Self : in out Item;   Low, High        : in Real;
+                                                Softness         : in Real := 0.9;
+                                                biasFactor       : in Real := 0.3;
+                                                relaxationFactor : in Real := 1.0)   is abstract;
+
+   function  lower_Limit (Self : in     Item)   return Real                          is abstract;
+   function  upper_Limit (Self : in     Item)   return Real                          is abstract;
+
+   function  Angle       (Self : in     Item)   return Real                          is abstract;
+
+end physics.Joint.hinge;