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From: agent@drrob1.com
Newsgroups: comp.lang.ada
Subject: confusing string error
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Date: Fri, 14 Feb 2014 07:38:10 -0500
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Xref: news.eternal-september.org comp.lang.ada:18551
Date: 2014-02-14T07:38:10-05:00
List-Id: <comp.lang.ada>

Code fragment:

type FSATyp is (delim, op, dgt, allelse);
type TokenType is record
  Ustr : unbounded_string;
  State : FSATyp;
  delimCH : Character;
  delimstate : FSATyp;
end record;

ch: character;

begin
 ...

Token.uStr := null_unbounded_string;

ch now contains a plus sign, or an asterisk
Token.uStr := Token.uStr & ch

this last line fails with error Ada.Strings.INDEX_ERROR

I don't understand this.  

When ch has a digit or an alphabetic character this code works.