String Manipulation

String Manipulation

[Howard Davies]

Hi,

Many thanks to the two guys who took the time to suggest packages and
functions I should look at to manipulate strings in Ada. It proved to be
a great help and helped me solve my problems.
Its good to know that there are still some decent folks around.

Thanks again
-- 
Howard Davies           Howard@roslyn.demon.co.uk

String Manipulation

[SiliconJesus]

I have run into a problem while writing a recent program.

I have a field in a record called name, which when I get input from a
specified data file it's Lastname, First well the problem is not in
inputting it, but when I update this record from another file, only the
last name is given.  So how do I read a character at a time and put only
the last name in a temp variable so I can compare the two names so that
the rest of the record gets updated.


Thanks


		
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==========================================================================

Re: String Manipulation

[David C. Hoos, Sr.]

SiliconJesus wrote in message ...
>I have run into a problem while writing a recent program.
<snip>

Look at the Find_Token procedure in Ada.Strings.Fixed

string manipulation

[Gep]

Is it possible to declare a string to be exactly 10 characters long and
still be a variable? then
for example

declare V_string as being exactly 10 characters


while not valid
loop
get_line(V_string, V_length);

if v_Art_lng = t_Art_article.t_art_proprietaire.v_nas'length then
      Skip_Line;
      Valid := True;
else
    valid :=false;
    Put("invalid");
end if;

end loop;

anything not in the range of declared string (in this case being10) would be
declared as invalid...any ideas?
I dont want to to have any explicit statement of 10 like "if V_length = 10
then"    in this little procedure as it will be getting strings of various
length.

Re: string manipulation

[Gep]

"Gep" <nodsa@sdfsffds.net> wrote in message
news:BhvI9.27495$Mn4.328936@wagner.videotron.net...
> Is it possible to declare a string to be exactly 10 characters long and
> still be a variable? then
> for example
>
> declare V_string as being exactly 10 characters
>
>
> while not valid
> loop
> get_line(V_string, V_length);
>
> if v_Art_lng = t_Art_article.t_art_proprietaire.v_nas'length then
>       Skip_Line;
>       Valid := True;
> else
>     valid :=false;
>     Put("invalid");
> end if;
>
> end loop;


oops the code should be as follows

 while not valid
loop
 get_line(V_string, V_length);

 if V_length= V_string'length then
      Skip_Line;
      Valid := True;
 else
     valid :=false;
     Put("invalid");
 end if;
end loop;

Re: string manipulation

[Jacob Sparre Andersen]

Gep wrote:
> Is it possible to declare a string to be exactly 10 characters long and
> still be a variable?

Yes:

    V_String : String (1 .. 10);

Jacob
-- 
"I don't want to gain immortality in my works.
  I want to gain it by not dying."

Re: string manipulation

[James S. Rogers]

"Gep" <nodsa@sdfsffds.net> wrote in message
news:BhvI9.27495$Mn4.328936@wagner.videotron.net...
> Is it possible to declare a string to be exactly 10 characters long and
> still be a variable? then

You want to use the package Ada.Strings.Bounded.
This package allows you to specify a maximum string length,
and use data up to that length.

Jim Rogers

Re: string manipulation

[Jeffrey Carter]

Gep wrote:
> 
>  while not valid
> loop
>  get_line(V_string, V_length);
> 
>  if V_length= V_string'length then
>       Skip_Line;
>       Valid := True;
>  else
>      valid :=false;
>      Put("invalid");
>  end if;
> end loop;

This looks better then that other code. You can do this. It will 
repeatedly get a line until it gets one that is exactly V_String'Length 
characters. If that's what you want. I don't see what it has to do with 
declaring a string variable of a specific length.

Valid is sort of useless here, as well as providing an opportunity for 
errors. You can forget to assign to it, or assign the wrong value. I 
think this would read better without it:

loop
    Get_Line (...);

    if V_Length = V_String'Length then
       Skip_Line;

       exit;
    end if;

    Put ("invalid");
end loop;

The purpose of the code is to exit the loop when a line of the right 
length is read. It's better for the code to say that, then to hide it 
behind a Boolean flag.

-- 
Jeff Carter
"Pray that there's intelligent life somewhere up in
space, 'cause there's bugger all down here on earth."
Monty Python's Meaning of Life

Re: string manipulation

[Marin David Condic]

It is technically possible, but the question seems to imply a bit of
confusion about the nature of the type String in Ada. String is a data type
that is an array - nothing more or less. Its element type is Character.
Hence, just as you can declare a type like:

type Vector is array (Integer range <>) of Float ;

and then make specific variables with specific numbers of elements:

My_Vector : Vector (1..10) ;
Your_Vector : Vector (20..50) ;

The exact same thing is legal in Ada for the type String. It is important to
understand that the 'Length doesn't have anything to do with the content of
the string - just the number of positions in the array.

The thing is that often programmers from other languages are used to strings
taking on dynamic sizes depending on what is assigned to them In C, it is
done - in a way - by including a null character somewhere in the array of
characters to indicate termination. This can be done in Ada as well, but is
highly unnatural and not recommended. If you are interested in strings with
a more dynamic nature, look at Ada.Strings.Bounded and Ada.Strings.Unbounded
in the ARM. (Also Ada.Strings.Fixed, if you want to deal with the standard
String type.) Both Bounded and Unbounded strings give you better ability to
look at the length of the string as a function of its content.

MDC
--
======================================================================
Marin David Condic
I work for: http://www.belcan.com/
My project is: http://www.jast.mil/

Send Replies To: m c o n d i c @ a c m . o r g

    "I'd trade it all for just a little more"
        --  Charles Montgomery Burns, [4F10]
======================================================================

Gep <nodsa@sdfsffds.net> wrote in message
news:ynvI9.27498$Mn4.329910@wagner.videotron.net...
>
> "Gep" <nodsa@sdfsffds.net> wrote in message
> news:BhvI9.27495$Mn4.328936@wagner.videotron.net...
> > Is it possible to declare a string to be exactly 10 characters long and
> > still be a variable? then
> > for example
> >
> > declare V_string as being exactly 10 characters
> >
> >
> > while not valid
> > loop
> > get_line(V_string, V_length);
> >
> > if v_Art_lng = t_Art_article.t_art_proprietaire.v_nas'length then
> >       Skip_Line;
> >       Valid := True;
> > else
> >     valid :=false;
> >     Put("invalid");
> > end if;
> >
> > end loop;
>
>
> oops the code should be as follows
>
>  while not valid
> loop
>  get_line(V_string, V_length);
>
>  if V_length= V_string'length then
>       Skip_Line;
>       Valid := True;
>  else
>      valid :=false;
>      Put("invalid");
>  end if;
> end loop;
>
>
>

Re: string manipulation

[Gep]

"Jeffrey Carter" <jrcarter@acm.org> wrote in message
news:3DF2AD96.6010100@acm.org...
> Gep wrote:
> >
> >  while not valid
> > loop
> >  get_line(V_string, V_length);
> >
> >  if V_length= V_string'length then
> >       Skip_Line;
> >       Valid := True;
> >  else
> >      valid :=false;
> >      Put("invalid");
> >  end if;
> > end loop;
>
> This looks better then that other code. You can do this. It will
> repeatedly get a line until it gets one that is exactly V_String'Length
> characters. If that's what you want. I don't see what it has to do with
> declaring a string variable of a specific length.
>
> Valid is sort of useless here, as well as providing an opportunity for
> errors. You can forget to assign to it, or assign the wrong value. I
> think this would read better without it:
>
> loop
>     Get_Line (...);
>
>     if V_Length = V_String'Length then
>        Skip_Line;
>
>        exit;
>     end if;
>
>     Put ("invalid");
> end loop;
>


What I wanted is a procedure that couldget both, a string with a fixed
length or a variable length. But it is ok I'm gonna done do two seprate
procedures. I thnik it is going to be more clear that way

thanks anyway for help.