## 12.2 Generic Bodies

(1)
The body of a generic unit (a generic body) is a template for the instance bodies. The syntax of a generic body is identical to that of a nongeneric body.
##### Dynamic Semantics
(2)
The elaboration of a generic body has no other effect than to establish that the generic unit can from then on be instantiated without failing the Elaboration_Check. If the generic body is a child of a generic package, then its elaboration establishes that each corresponding declaration nested in an instance of the parent (see 10.1.1) can from then on be instantiated without failing the Elaboration_Check.

NOTES
(3)
(4) The syntax of generic subprograms implies that a generic subprogram body is always the completion of a declaration.
##### Examples
(4)
Example of a generic procedure body:
```(5)
procedure Exchange(U, V : in out Elem) is  -- see 12.1
T : Elem;  --  the generic formal type
begin
T := U;
U := V;
V := T;
end Exchange;
```
(6)
Example of a generic function body:
```(7)
function Squaring(X : Item) return Item is  --  see 12.1
begin
return X*X;  --  the formal operator "*"
end Squaring;
```
(8)
Example of a generic package body:
```(9)
package body On_Vectors is  --  see 12.1
(10)
function Sum(A, B : Vector) return Vector is
Result : Vector(A'Range); --  the formal type Vector
Bias   : constant Integer := B'First - A'First;
begin
if A'Length /= B'Length then
raise Length_Error;
end if;
(11)
for N in A'Range loop
Result(N) := Sum(A(N), B(N + Bias)); -- the formal function Sum
end loop;
return Result;
end Sum;
(12)
function Sigma(A : Vector) return Item is
Total : Item := A(A'First); --  the formal type Item
begin
for N in A'First + 1 .. A'Last loop
Total := Sum(Total, A(N)); --  the formal function Sum
end loop;
return Total;
end Sigma;
end On_Vectors;
```

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