1package body Geometry.Magic is
2
3 function Moment(OC : Object'Class) return Float is
4 -- This is class wide since the same formula applies to all
5 -- types. Note that it illustrates both the inheritance of a
6 -- component (X_Coord) and an operation (Area). The call of
7 -- Area is a dispatching call. It is assumed that the units
8 -- are such that the Mass equals the Area and that the
9 -- acceleration due to gravity (g) is 1.
10 begin
11 return OC.X_Coord * Area(OC);
12 end Moment;
13
14 function MO(OC : Object'Class) return Float is
15 -- This is also class wide since again the same formula
16 -- applies to all types.
17 -- It uses the so-called parallel axis theorem that the
18 -- moment of inertia about another point (here the origin)
19 -- equals the sum of the moment of inertia about the center of
20 -- gravity (MI) plus the Mass times the square of the distance
21 -- of the center of gravity from the origin. Remember that
22 -- the units are such that the Mass equals the Area.
23 -- The calls of MI, Area and Distance are dispatching calls.
24 begin
25 return MI(OC) + Area(OC) * Distance(OC)**2;
26 end MO;
27
28end Geometry.Magic;