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From: ncohen@watson.ibm.com (Norman H. Cohen)
Newsgroups: comp.lang.ada
Subject: Re: Ada.strings.bounded problems?
Date: 12 Jan 1995 18:16:07 GMT
Organization: IBM T.J. Watson Research Center
Distribution: world
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References: <TARJEIJ.95Jan11183331@ulrik.uio.no> <D29L78.J9@nntpa.cb.att.com>
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Date: 1995-01-12T18:16:07+00:00
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In article <D29L78.J9@nntpa.cb.att.com>, ka@socrates.hr.att.com
(Kenneth Almquist) writes: 

|> Tarjei Jensen <tarjeij@ulrik.uio.no> wrote: 

|> This is definitely a weakness of Ada.  There is no way to implement a
|> single bounded string type that can be constrained to implement various
|> maximum string lengths.  It would not be too hard to add a bounded
|> arrays (a generalization of bounded string) to Ada, but I don't recommend
|> it, given the current complexity of Ada.

This is definitely a weakness of Jensen's understanding of Ada.

There IS a way to implement bounded strings with the bound given as a
constraint, so simple that it is found in many introductory examples: 

   package Bounded_Strings is
      type Bounded_String (Max_Length: Positive) is private;
      ...  -- all sorts of useful operations
   private
      type Bounded_String (Max_Length: Positive) is
        record
           Current_Length : Natural := 0;
           Text           : String (1 .. Max_Length);
        end record;
   end Bounded_Strings;

This approach is easily generalized to other kinds of arrays.

--
Norman H. Cohen    ncohen@watson.ibm.com