Re: Enumeration_IO

[mfeldman@seas.gwu.edu (Mike Feldman)]

In article <1874@gould.doc.ic.ac.uk> umace03@doc.ic.ac.uk (M Y Ben Gershon) writes:
>
>>In article <1850@sparko.gwu.edu> mfeldman@seas.gwu.edu (Mike Feldman) writes:
>
>>      COLOR_IO.PUT(ITEM => C, SET => TEXT_IO.LOWER_CASE);
>>                                     ^^^^^^^^
>
>Yes, OK.  But why doesn't COLOR_IO.LOWER_CASE work, seeing that we are using
>
>package COLOR_IO is new TEXT_IO.ENUMERATION_IO(ENUM => COLORS);
>
>shouldn't it follow that LOWER_CASE is distinct for each separate instantiation
>of TEXT_IO.<enum_type> ?  Yet, if I put COLOR_IO.LOWER_CASE it doesn't work,
>giving the same error message as before.

Well, now that I'm such an expert, this one is easy. It's because the
enumeration type TYPE_SET (which contains the literals UPPER_CASE and
LOWER_CASE) is exported from TEXT_IO (i.e. the outer layer) and NOT from
any of the enclosed generic packages. Checking the LRM or a good text's
appendix for the full spec of TEXT_IO will confirm this. So there's really
only one set of literals, and it ain't exported from COLOR_IO!

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Prof. Michael Feldman
Department of Electrical Engineering and Computer Science
The George Washington University
Washington, DC 20052
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mfeldman@seas.gwu.edu
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