Borland Pascal “open array” formal parameters are implemented into GPC. Within the function body, they have integer type index with lower bound 0.
In constrast to conformant arrays (which are not supported by BP),
open arrays allow any ordinal type as the index of the actual
parameter (which is useful, e.g., if you want to be able to pass
values of any enumeration type). However, they lose information
about the lower bound (which is a problem, e.g., if you want to
return information to the caller that relates to the actual array
index, like the function IOSelect
in the Run Time System
does).