An assertion directive is an alternative to a macro
definition, used to define the computer or system the compiled program
will run on. Assertions are usually predefined, but you can define
them with the #assert preprocessor directive.

#assert directive syntax
>>-#--assert--predicate--(--answer--)--------------------------><
The
predicate represents the assertion entity you
are defining. The
answer represents a value you are assigning
to the assertion. You can make several assertions using the same predicate
and different answers. All the answers for any given predicate are
simultaneously true. For example, the following directives create
assertions regarding font properties:
#assert font(arial)
#assert font(blue)
Once an assertion has been defined, the assertion predicate
can be used in conditional directives to test the current system.
The following directive tests whether
arial or
blue is
asserted for
font:
#if #font(arial) || #font(blue)
You
can test whether any answer is asserted for a predicate by omitting
the answer in the conditional:
#if #font
Assertions can be cancelled with the
#unassert directive.
If you use the same syntax as the
#assert directive,
the directive cancels only the answer you specify. For example, the
following directive cancels the
arial answer for
the
font predicate:
#unassert font(arial)
An entire predicate is cancelled by omitting the answer
from the
#unassert directive. The following directive
cancels the
font directive altogether:
#unassert font