Re: output of enumeration types

["Staszek Goldstein" <goldstei@math.uni.lodz.pl>]

Uzytkownik "Stephen Leake" <stephen_leake@acm.org> napisal w wiadomosci 
news:mailman.54.1113954069.24457.comp.lang.ada@ada-france.org...
> "Staszek Goldstein" <goldstei@math.uni.lodz.pl> writes:
>
>> This
>
> please quote enough so we can tell what you are refering to.

My letter was an answer to a specific message containing just one idea.

>> is also a nice idea, although for converting a string you still need
>> a function like the one given by Stephen Leake. It seems to me that
>> it should be possible to output the roman number as easily as it is
>> to output a string - there is no difference between the literals,
>> they both look exactly the same.
>
> As far as I can see, it is "just as easy". There is a package, that
> someone wrote, that does text output for type String. Since you are
> writing a new type, you need to write the output package for that as
> well. Once that is done, both are "just as easy" for anyone else to
> use.
>
> Note that Character has a special place in this discussion, since by
> definition it is what gets written to a "text" file.
>
> So to do "output" with Roman_Number, you must specify some way to
> convert its components to Character.

I do not feel convinced by the argument. If you want to write a number, you 
can qualify it
to be of some specific type and output it using, say, some instantiation of 
the
ada.text_io.integer_io package. Although the situation is very similar 
here - I just want to be
able to output character literals or arrays of such literals, I have no 
generic package at
my disposal and no possibility of converting them directly to the 
"character" or "string" type.

> Here's another tidbit that points out why "universal character" wont
> solve this problem:
>
>   type Roman_Digit is (Foo,'V','X','L','C','D','M');
>
> is a perfectly legal type declaration!

I am not sure if this is really a problem. If 'V' is of a "universal 
character type", then it is directly
convertible to any character type which contains it as an enumeration 
literal. Also, writing
character(rm), where rm is a roman digit, should do no harm - this should 
raise constraint_error
or program_error if rm is not a character literal. More or less the same is 
true of
integer(long_int)... By the way, I have not experienced many applications of 
the "mixed" types
up to now.

Staszek