Re: How to delete charcters in a string?

[Larry Hazel <lhhazel@otelco.net>]

Ted Dennison wrote:
> 
> "Anthony Wise" <iamwisey_@hotmail.com> wrote in message news:<mailman.1012350362.32618.comp.lang.ada@ada.eu.org>...
> > (im new to ada by the way)
> >
> > well supose there is a character in a string which i do not want to be seen
> > in the output.  i don't want to change it to anouther character but delete
> > it completely.
> 
> I've seen a lot of answers, but I'll throw mine in anyway because I
> think there's a point that needs to be made.
> 
> Ada strings are *very* different from C strings, and it takes a bit of
> getting used to. In C, strings are essentially a sequence of CHARs
> with a null (0) at the end. In Ada, strings are an array of characters
> of an exact range that *you* specify (by default, the entire array).
> The string ends where your array (or slice of the array) ends. In
> practice strings rarely change, so you can set your string to
> perfectly fill the array, which makes Ada strings much easier to deal
> with (and quicker) than their C counterparts. In the rare cases where
> strings do change, you must keep a length index separately, or use one
> of the alternate dynamic string types in Ada.Strings.*.
> 
> If you are using the String type for your strings, realize that these
> strings are "fixed", and are best dealt with that way. That means that
> rather than trying to remove a character, what you generally would
> look to do is create a new string value (separate from the old one)
> with the character removed. There's a routine in Ada.Strings.Fixed to
> help with that, but if you know its index its just as easy to do it
> with something like:
>   My_String (My_String'first .. Char_Index - 1) &
>   My_String (Char_Index + 1 .. My_String'last);
> 
> However, I should say that solutions to this problem should go on the
> back burner until you have dicovered that you are solving the right
> problem in the first place. Perhaps you are, but often newbies are
> not, and there's no ways to tell from your post. Since Ada and C
> strings are so different, the techniques you may have learned for
> dealing with dynamic C strings are liable to be completely
> inappropriate for dealing with fixed Ada strings. So the first
> question we need answered is *why* you want to remove a character from
> the middle of your string.
> 
Good points Ted.  It caused me to wonder.  Since a null character in Ada means
(essentially) "no character here", rather than end of string, could you just
replace the character you want to delete with a null character?

Larry