Static assertions

["Jean-Pierre Rosen" <rosen@adalog.fr>]

Still discovering how powerful Ada is...

Imagine your program relies on Integer having a certain size, or being sure
that the size of Integer is four times the size of character, or things like
that, and you want to make sure that the program does not even compile if
the assertions do not hold (because you hate fighting with a debugger). This
is possible, since a static expression that raises constraint_error will not
compile. Just include something like the following package:

package Verifier is
   subtype Assert is Boolean range True..True;

   Assert_1 : constant := Boolean'Pos( Assert (Integer'Size=32) );
   Assert_2 : constant := Boolean'Pos( Assert
(Integer'Size=4*Character'Size) );
end Verifier;

(The Boolean'Pos serves to have a value used in a named number declaration,
which requires a static context).
--
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           J-P. Rosen (rosen@adalog.fr)
Visit Adalog's web site at http://www.adalog.fr