Add initial prototype.

1-base/math/source/generic/pure/geometry/trigonometry/cached_rotation.adb

@@ -0,0 +1,43 @@
+package body cached_Rotation
+is
+   use ada.Numerics,
+       float_elementary_Functions;
+
+
+   the_Cache       : array (0 .. slot_Count - 1) of aliased Matrix_2x2_type;
+
+   Pi_x_2          : constant            := Pi * 2.0;
+   last_slot_Index : constant Float_type := Float_type (slot_Count - 1);
+   index_Factor    : constant Float_type := last_slot_Index / Pi_x_2;
+
+
+
+   function to_Rotation (Angle : in Float_type) return access constant Matrix_2x2_type
+   is
+      the_Index : standard.Integer := standard.Integer (Angle * index_Factor) mod slot_Count;
+   begin
+      if the_Index < 0
+      then
+         the_index := the_Index + slot_Count;
+      end if;
+
+      return the_Cache (the_Index)'Access;
+   end to_Rotation;
+
+
+
+begin
+   for Each in the_Cache'Range
+   loop
+      declare
+         Angle : constant Float_type := (  Float_type (Each) / Float_type (slot_Count - 1)
+                                         * Pi_x_2);
+
+         C : constant Float_type := Cos (Angle);
+         S : constant Float_type := Sin (Angle);
+      begin
+         the_Cache (Each) := to_Matrix_2x2 (C, -S,
+                                            S,  C);
+      end;
+   end loop;
+end cached_Rotation;