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From: Mark Griglock <mark.griglock@lmco.com>
Subject: Re: What's the deal with "slice" in Ada.Strings.Bounded
Date: 1997/07/15
Message-ID: <33CC07BB.7F52@lmco.com>#1/1
X-Deja-AN: 257084486
References: <33CBDCDF.751F5ECB@digicomp.com>
Organization: Lockheed Martin Federal Systems
Reply-To: mark.griglock@lmco.com
Newsgroups: comp.lang.ada
Date: 1997-07-15T00:00:00+00:00
List-Id: <comp.lang.ada>


Jan Galkowski wrote:
> 
> The package Ada.Strings.Bounded operates upon a private type
> "Bounded_String".  Among the other constructors and manipulators
> in that package, there is an interrogator called "Slice".
> 
> What I'm trying to figure out is how to create a Bounded_String
> out of the return value from this "Slice".  The type
> given for the return value is the general "String".  Naturally,
> compilers balk at trying to specify a variable having definite
> dimensions using an object which has indefinite ones.
> 
> So, how would you suggest making a Bounded_String out of this
> return value from "Slice"?  In other words, how does one
> write, for this case, a function
> 
>    function To_Bounded_String( Given_String : in String )
>       return Bounded_String is
>     ...
>    begin
>     ...
>    end To_Bounded_String ;
> 
> where Bounded_String has been given a fixed length by instantiating
> "Generic_Bounded_Length".
> 
The above function already exists in Generic_Bounded_Length, (it does,
however, have a second parameter with a default).  It is also called
To_Bounded_String.  For example, you could write the following specific
function:

  package Bounded_80 is new 
Ada.Strings.Bounded.Generic_Bounded_Length(80);

 function Slice_80
    (Source : in Bounded_80.Bounded_String;
     Low    : in Positive;
     High   : in Natural)
     return Bounded_80.Bounded_String is
  begin
    return Bounded_80.To_Bounded_String
      (Bounded_80.Slice(Source, Low, High));
  end Slice_80;

Or, if you needed this for all Bounded_Length strings, you can make it
generic:
  
  generic
    with  package Bounded is new 
Ada.Strings.Bounded.Generic_Bounded_Length(<>);

  function Slice 
    (Source : in Bounded.Bounded_String;
     Low    : in Positive;
     High   : in Natural)
     return Bounded.Bounded_String;

  function Slice 
    (Source : in Bounded.Bounded_String;
     Low    : in Positive;
     High   : in Natural)
     return Bounded.Bounded_String  is
  begin
    return Bounded.To_Bounded_String
      (Bounded.Slice(Source, Low, High));
  end Slice;

Sorry, if I misunderstood the question...