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NNTP-Posting-Date: Wed, 29 Nov 2006 12:09:44 -0600
From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: Strings and errors... (gnat)
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Date: Wed, 29 Nov 2006 19:10:22 +0100
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Date: 2006-11-29T19:10:22+01:00
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tr00per writes:
> Robert A Duff napisal(a):
>> You can't assign a shorter string into a longer one -- the lengths have
>> to match.  You could do:
>>
>>     tmp: String := buf(13..26);
>>
>> or
>>
>>     tmp: constant String := buf(13..26);
>>
>> and it will take the bounds for tmp from buf(13..26).
>>
>> Or, you could use Unbounded_Strings.
>>
>> - Bob
>
> Actual length of the string is dependend on other data, range here is
> for example, so these declarations aren't solution for me, but thanks
> anyway. Maybe there is a ready-to-use function for splitting the string
> by template, so I don't have to reinvent the wheel?
> I have input in format String:String:String. I want to get rid of these
> colons and get three seperate strings.

Robert's advice still holds:

1) the bounds of a String can be dynamic, so you can also say
   tmp : constant String := buf (A .. B); -- A and B computed from input

2) You can use Ada.Strings.Unbounded.

Now for my own advice:

1) Look at Ada.Strings.Fixed.Find_Token.  It will help you find the
   colons.

2) Look at Ada.Strings.Bounded; it is more efficient than
   Unbounded_Strings, but you have know the maximum length in advance.

3) If you are writing a subprogram that splits a given string into 3
   strings of unknown length, you have basically 4 options:

   a) return 3 access values to dynamically allocated strings
   b) return 3 unbounded strings
   c) return 3 bounded strings
   d) return 3 fixed strings and 3 Last values, like
      Ada.Text_IO.Get_Line does.

But simply returning 3 fixed strings will not work.

-- 
Ludovic Brenta.