Figure 27.
Constrained objects can't change constraints.
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-- This procedure illustrates thee consequences of LRM
-- Section 3.2.1 paragraph 12.
procedure Constrained_Objects_Cant_Change_Constraints is
type No_default (LENGTH : natural) is
record
TEXT : string(1..LENGTH);
end record;
type Default (LENGTH : natural := 0) is
record
TEXT : string(1..LENGTH);
end record;
FIRST_NAME : No_default(8);
WHOLE_NAME : Default(14);
LAST_NAME : Default;
begin
-- I can let LAST_NAME hold a 5 character name.
LAST_NAME := (LENGTH => 5, TEXT => "Jones");
-- Then I can stretch it to hold a 10 character name.
LAST_NAME := (10, "Washington");
-- FIRST_NAME can hold an 8 character name.
FIRST_NAME := (8, "Do-While");
-- But it can't shrink to hold a shorter one
-- because it was constrained to be 8 characters
-- when it was declared.
FIRST_NAME := (4, "Dave"); -- ILLEGAL
-- You might think WHOLE_NAME can be changed because
-- it has a default length, but the fact is it was
-- constrained to be 14 characters when it was
-- declared, so it can't be changed either.
WHOLE_NAME := (17, "George Washington"); -- ILLEGAL
end Constrained_Objects_Cant_Change_Constraints;
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