Re: Ada Recursion with strings

[Adam Beneschan <adam@irvine.com>]

On Sep 30, 1:30 pm, Joe <joesmo...@gmail.com> wrote:
> Hey all,
> I'm trying to write a function that converts a 2**32 mod type into an
> string formatted like an IP address (i.e. 192.168.2.1).
>
> Here's what I wrote
>
> with Ada.Text_IO;
> use  Ada.Text_IO;
>
> procedure Ip_packet is
>    type Word_Type is mod 2**32;
>
>    function IP_String (Word : Word_Type;
>                        IP_String : String := "") return String
> is
>       Sub_String : String := Word_Type'Image(Word mod 2**8);
>    begin
>       if Word <= 2**8 then
>          return Word_Type'Image(Word) & IP_String;
>       else
>          return IP_String( Word / 2**8,
>                            "." & Sub_String & IP_String);
>       end if;
>    end IP_String;
>
> begin  --  Ip_packet
>    Put(IP_String(123456));
> end Ip_packet;
>
> There are 2 errors with this that I don't understand.  First, Ada
> expects an integer for (word / 2**8).  Is this because word_type is
> outside the standard integer range?  How do I get a division operator
> that works on word_type?
>
> If I patch the integer error by type casting word to an integer I get
> another error.  On the second return statement, Ada complains that
> there are "too many subscripts in array reference".  Is there a
> limitation on the string I can pass to a recursive function call?

When you say this:

        return IP_String( Word / 2**8,
                          "." & Sub_String & IP_String);

what is the compiler going to think you mean by the first IP_String in
this expression?  What about the second one?

There are other errors in your code; you'll probably figure several of
them out once you get your program to run, and you'll probably figure
another out if you change 123456 in your test to 65536.

                              -- Adam