%IF Statement
The %IF statement controls the flow of the scan according
to the bit value of a preprocessor expression.
 >>-%--+------------+--IF--preprocessor-expression--%--THEN------>
| .--------. |
| V | |
'---label:-+-'
>--preprocessor-unit1--+-----------------------------+---------><
'-%--ELSE--preprocessor-unit2-'
|
- preprocessor-expression
- Is evaluated and converted to a bit string (if the conversion
cannot be made, it is an error).
- preprocessor-unit
- Is any single preprocessor statement (other than %DECLARE, %PROCEDURE, %END,
or %DO) a preprocessor DO-group, or a preprocessor SELECT-group. Otherwise,
the description is the same as that given under IF statement.
If any bit in the string has the value '1'B, unit1 is executed
and unit2, if present, is ignored; if all bits are '0'B, unit1 is
ignored and unit2, if present, is executed.
Scanning resumes immediately following the %IF statement,
unless, of course, a %GO TO or preprocessor RETURN statement
in one of the units causes the scan to resume elsewhere.
%IF statements can be nested in the same manner used
for nesting IF statements, as described under IF statement.
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