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Path: utzoo!utgpu!water!watmath!clyde!rutgers!seismo!mcvax!enea!sommar
From: sommar@enea.UUCP
Newsgroups: comp.lang.ada
Subject: Characters with codes >= 128
Message-ID: <2231@enea.UUCP>
Date: Sun, 30-Aug-87 17:28:05 EDT
Article-I.D.: enea.2231
Posted: Sun Aug 30 17:28:05 1987
Date-Received: Tue, 1-Sep-87 04:16:53 EDT
Reply-To: sommar@enea.UUCP(Erland Sommarskog)
Followup-To: comp.lang.ada
Organization: ENEA DATA Svenska AB, Sweden
List-Id: <comp.lang.ada>


I'd like to write a programme that can handle text which contains
characters from an extented ASCII set for covering national 
characters. The LRM seems to totally disregard this, since it
states that the character type is ASCII with 128 possible values.
Also, Ada only allows you to have printable characters within
strings. And printable is defined as the range ' '..'~'. 
  Easy, you might say. Just define a new character type. How?
I can't have quoted strings for the new characters, since they
are "non-printing". I can't extend the ASCII package (in STANDARD),
since it relies on that the character type is already defined.
  And even if I succeed somhow, how to with Text_io? Will the 
compiler accept attempt to give Text_io the new character type,
even if it's called "character"? Hardly.
  Have I missed someting? I hope. If not, THIS IS A VERY SERIOUS
RESTRICTION IN ADA.

I should add that to some extent it is possible to handle these
characters. My Ada system (Verdix 5.2A for VAX/Unix) doesn't mind
if I read an extended character from a file or if I try to write
it. Character'val(ch) on the character returns the correct code.
But Character'pos(Character'val(ch)) raises Contraint_error if
ch is from the upper half.
  But this only a little. I want string constants in my programme,  
it's dead. What do? Read them from a file at start-up? :-)
-- 

Erland Sommarskog       
ENEA Data, Stockholm    
sommar@enea.UUCP