Re: design problem/?

[GBOOCH@USC-ECLB.ARPA]

For a heavilylayered system in which abstractions are built on
top of abstractions (and each layer hids its implementation), I tend to
use either access types (occasionally) or derived types (most often).

thus, in your example of the package file_stuff, I would probably write
the full type declaration for a_file as:

type a_file is new text_io.file_type;

This actually is a common issue (i.e. how tdo I get the implementation of
a private type to map excatly to another type). It would be
nice (sometimes) to have a fully type declaration in the private part
as a subtype, rather than a type, but Ada prevents this (and for
good reason, I believe...the alternative produces some strnage
problems).

egb
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