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From: Ehud Lamm <mslamm@mscc.huji.ac.il>
Subject: Re: String Length
Date: 1998/10/02
Message-ID: 
 <Pine.A41.3.96-heb-2.07.981002184423.80238D-100000@pluto.mscc.huji.ac.il>#1/1
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References: <36140400.0@news.cyberenet.net> <6v2ggj$p73$1@cf01.edf.fr>
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Organization: The hebrew University of Jerusalem
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Newsgroups: comp.lang.ada
Date: 1998-10-02T00:00:00+00:00
List-Id: <comp.lang.ada>

First let me give two approaches that work:

--  CODE FOLLOWS
with ada.strings.unbounded; use ada.strings.unbounded;
procedure try_strings is
   
  s:string := "ehud lamm";
begin

   put(s'length);
   put(length(to_unbounded_string("ehud")));
   
    
end;
-- END OF CODE

There are huge diffrences between the two methods used above. The second
way (converting to an unbounded string) is costlier in any respect. I urge
you to understand this.

The first solution, using the attribute 'length on a String type variable
is nice, since it results in a static expression. One confusing detail may
be, that since String itself is an indefinite type (it is basically an
unconstraint array type), you can not do something like this:

-- WARNNING BAD CODE AHEAD
s:String
i:iinteger;
begin
  s:="ehud";
  i:=s'length;
end;
-- SAFE AGAIN

You simply can not declare variables of type string without contraining it
to some fixed length. When you say s:string:="ehud", the complier knows
the length needed for s, by looking at the initialization.

One final note: You can not say: "ehud"'length. This attribute will not
work on a value, it wants a variable.


Hope this helps!

Ehud Lamm     mslamm@pluto.mscc.huji.ac.il