Novice String Question

Novice String Question

[Ray]

I am working on learning strings, so forgive the creaky code.
I can get the �Replace_Slice� to work if Y and Z are the same length,
otherwise the last Put_Line will raise an exception.

1. Do I need, and how can I get the Drop and Justify parameters to work?
2. Should I be using something else?
3. How can I convert this to either bounded or unbounded (have not been
able to get the declares/withs right)?


-- code
with Ada.Text_Io, Ada.integer_text_io, Ada.Strings.Fixed;
use Ada.Text_Io, Ada.integer_text_io, Ada.Strings.Fixed;

--
-- Cohen 'Ada as a 2nd language' 2nd ed.  Page 225.
-- Exercise 5.2, read a source X, pattern Y, and replace Z strings.
-- Replace the first occurrence of the pattern.
-- Assume max string length is 80.
--
procedure EX5_2 is
   X, Y, Z: string (1 .. 80);
   I_X, I_Y, I_Z : Natural;

begin
   get_line (X, I_X);             -- get the strings
   get_line (Y, I_Y);
   get_line (Z, I_Z);
                                  -- find start of first match
   Flag_InStr := Index(X(X'first .. I_X), Y (Y'first .. I_Y));

   If Flag_InStr /= 0 then        -- do we have a match?
     X := Replace_Slice
       (X,
        Flag_InStr,
        Flag_InStr + I_Y - 1,
        Z(Z'first .. I_Z));

     I_X := I_X + (I_Z - I_Y);  -- correct X end index for Z and Y not =
length
   end if;

   put_line (X (X'first .. I_X));  -- echo the modified string

end EX5_2;


--
Remove the numbers from my address to reply.

Ray