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From: fmdf@tiscali.it (fabio de francesco)
Newsgroups: comp.lang.ada
Subject: variable lenght strings
Date: 21 Oct 2004 10:52:55 -0700
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Date: 2004-10-21T10:52:55-07:00
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Hi,

while studying from "Ada as a 2nd Language" I am having some problem
to cope with Strings (Fixed, Unbounded and Bounded) manipulation and
especially with assigning between different types of them and with
overall with input/output.

1) Is it possible to use Get_Line with Unbounded and/or Bounded
Strings?

2) If not, how should user input be managed when lines length isn't
known a priori?

3) I have to write a program that parses a file in which there are
lines that have to be "tokenized". I didn't find any Find_Token()
usage example on the Book so I wrote a little piece of code in order
to understand the procedure workings on a fixed string (Line A) that
simulates file input.

Think that I am used with C function strtok() and I must say that Ada
Find_Token is much more elegant and not destructive as strtok() is.

Ok, please let me know if the following is the correct usage:


with Ada.Text_IO, Ada.Strings, Ada.Strings.Fixed, 
    Ada.Strings.Maps, Ada.Strings.Maps.Constants;
use Ada.Text_IO, Ada.Strings, Ada.Strings.Fixed,
    Ada.Strings.Maps, Ada.Strings.Maps.Constants;

procedure Tokenize is
        
    S : constant String := ".symbol HP = High_Pressure    "; -- Line A
    F : Positive := S'First;
    L : Natural := S'Last;
    W : String( 1..30 );
        
begin
  loop
    Find_Token(S(F..L), Alphanumeric_Set or To_Set("_."), Inside, F,
L);
    if L /= 0 then
       Put_Line( Positive'Image( F ) & ( L - F ) * ' ' &
Natural'Image( L ) );
         Move( S( F..L ), W );
         Put_Line( ' ' & W );
         F := L + 1;
         L := S'Last;
    else 
       exit;
    end if;
  end loop;      
end Tokenize;


Is it correct to check the "L" value as a condition to exit the loop?


Thank you in advance for any help,

Fabio De Francesco