Syntax:
pragma Pre_Class (Boolean_Expression);
The Pre_Class pragma is intended to be an exact replacement for
the language-defined
Pre'Class aspect, and shares its restrictions and semantics.
It must appear either immediately following the corresponding
subprogram declaration (only other pragmas may intervene), or
if there is no separate subprogram declaration, then it can
appear at the start of the declarations in a subprogram body
(preceded only by other pragmas).
Note: This pragma is called Pre_Class rather than
Pre'Class because the latter would not be strictly
conforming to the allowed syntax for pragmas. The motivation
for providing pragmas equivalent to the aspects is to allow a program
to be written using the pragmas, and then compiled if necessary
using an Ada compiler that does not recognize the pragmas or
aspects, but is prepared to ignore the pragmas. The assertion
policy that controls this pragma is Pre'Class, not
Pre_Class.