When you use multidimensional arrays, make sure the subscript for each
dimension is consistent with its declared type. If any subscript value is out
of range, Constraint_Error will be raised, of course.
If you use nested FOR loops to process the array elements, make
sure that loop control variables used as array subscripts are in the correct
order. The order of the loop control variables determines the sequence in which
the array elements will be processed.
Understanding variant records is not always easy. In defining variant record structures, remember that the only way to allow for changing the variant stored in a variant record variable is to supply a default value for the discriminant. This action makes the variable unconstrained.
In using variant record variables, keep in mind that the value of the
discriminant field determines the form of the variant part that is currently
defined; attempting to manipulate any other variant will cause either a
compilation error or the raising of Constraint_Error. It is the
programmer's responsibility to ensure that the correct variant is being
processed; consequently, a variant record should always be manipulated in a
CASE statement with the discriminant field used as the
CASE selector to ensure that the proper variant part is being
manipulated.
Copyright © 1996 by Addison-Wesley Publishing Company, Inc.