Re: Enumeration_IO

[umace03@doc.ic.ac.uk (M Y Ben Gershon)]

Newsgroups: comp.lang.ada
Subject: Re: Enumeration_IO
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References: <1846@sparko.gwu.edu>
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Reply-To: umace03@doc.ic.ac.uk (M Y Ben Gershon)
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Organization: Imperial College Department of Computing
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In article <1846@sparko.gwu.edu> mfeldman@seas.gwu.edu (Mike Feldman) writes:
>In preparing some programs for a book I am working on, I have gotten
>interested in the idiosyncracies of Enumeration_IO. Specifically, the
>PUT operations in this generic package are supposed to have a parameter
>SET of type TYPE_SET, where TYPE_SET is (LOWER_CASE, UPPER_CASE).
>
>Well, consider an enumeration type
>  type COLORS is (red, blue, green);
>and an instance 
>  package COLOR_IO is new TEXT_IO.ENUMERATION_IO(ENUM => COLORS);
>and a variable
>  C : COLORS := blue;
>and an output operation
>  COLOR_IO.PUT(ITEM => C);
>
>All is well so far, everything compiles and runs except that the output
>value is BLUE, because the default is Upper_Case. Now change the output
>operation to
>  COLOR_IO.PUT(ITEM => C, SET => LOWER_CASE);
>
>Irvine Ada (HP835), IntegrAda (IBM-PC), VADS (Sun3) and AdaVantage (Sun3)
>ALL bail out on a "LOWER_CASE is an undefined identifier" diagnostic.
>Clearly something is going on here. According to LRM 14.3.9 this should be
>allowed. Can anyone provide some enlightenment here?



I can't claim to be an Ada expert, but altering it to the following:

  Color_IO.Put (Item => C, Set => Text_IO.Lower_Case);

seems to work fine in AdaStudent.  Alternatively, you could leave it unchanged
and have a 'use Text_IO' at the top, after 'with Text_IO'.  However, it
doesn't quite seem to make sense, and if the following is tried:

  Color_IO.Put (Item => C, Set => Color_IO.Lower_Case);

it doesn't work (as in the original example).  Why this should be I cannot
imagine, but when someone can explain it to us on the net, I'm sure we'll all
have learned something about generic packages that we didn't know before.

Michael Ben-Gershon
umace03@doc.ic.ac.uk