Object-oriented Software in Ada 95

202 Child libraries
14.6 A generic procedure to sort data
A generic sort procedure using the above variation of the bubble sort algorithm has the following specification:
generic
type T is private; --Any non limited type
type Vec_Range is (); --Any discrete type
type Vec is array( Vec_Range ) of T;
with function ">"( First, Second:in T ) return Boolean is ;
procedure Sort( Items:in out Vec );
The generic formal parameters for the procedure Sort are:
Formal parameter
type T is private;
type Vec_Range is ();
type Vec is array( Vec_Range ) of T;
with function ">"(First,Second:in T)
return Boolean is ;
Description
The type of data item to be sorted.
The type of the index to the array.
The type of the array to be sorted.
A function that the user of the
generic procedure provides to
compare pairs of data items.
The implementation of the generic procedure is:
procedure Sort( Items:in out Vec ) is
Swaps : Boolean := True;
Tmp : T;
begin
while Swaps loop
Swaps := False;
for I in Items'First .. Vec_Range'Pred(Items'Last) loop
if Items( I ) > Items( Vec_Range'Succ(I) ) then
Swaps := True;
Tmp := Items( Vec_Range'Succ(I) );
Items( Vec_Range'Succ(I) ) := Items( I );
Items( I ) := Tmp;
end if;
end loop;
end loop;
end Sort;
Note:
Passes through the data are repeated until there are no more swaps.
The use of 'Succ delivers the next index. Remember the array might have an index of an enumeration
type, so + cannot be used.
© M A Smith - May not be reproduced without permission