Attempt to build the Ada Rosetta Code "Caesar cipher" Task fails

General
1

Hi;

I am unable to build the Ada Rosetta Code Caesar cipher Task.

Caesar cipher - Rosetta Code

—+++++++++++++++++++++++++++++++++++++++++++++++++
/opt/gcc-13.2.0-aarch64/bin/gnatmake
gcc -c -I./ -I- ./caesar.adb
caesar.adb:7:24: error: “modulo” is undefined
caesar.adb:7:30: error: missing “;”
caesar.adb:14:31: error: subprogram “modulo26” cannot be used before end of its declaration
caesar.adb:16:39: error: prefix of “Pos” attribute must be a type
caesar.adb:19:39: error: subprogram “modulo26” cannot be used before end of its declaration
caesar.adb:24:35: error: subprogram “modulo26” cannot be used before end of its declaration
caesar.adb:26:35: error: subprogram “modulo26” cannot be used before end of its declaration
caesar.adb:35:08: error: subprogram “modulo26” cannot be used before end of its declaration
gnatmake: “./caesar.adb” compilation error
Build failed.
—+++++++++++++++++++++++++++++++++++++++++++++++++

Is this a coding error in the Rosetta Code Task or is it that it worked in an earlier version of Ada or a different Ada compiler?

Thanks,
Retired Build Engineer

2

That’s a horror, not near to be valid Ada. It seems a joke or something machine-generated, but then, not very current. Bing copilot was able to generate this near valid implementation:

-- Caesar Cipher Implementation in Ada

with Ada.Text_IO;
use Ada.Text_IO;

procedure Caesar_Cipher is
   -- Function to encrypt a character
   function Encrypt_Char(Char_To_Encrypt: Character; Shift: Integer) return Character is
      begin
         if Char_To_Encrypt in 'A'..'Z' then
            -- Only encrypt uppercase letters
            return Character'Val((Character'Pos(Char_To_Encrypt) + Shift - Character'Pos('A')) mod 26 + Character'Pos('A'));
         else
            -- Leave other characters unchanged
            return Char_To_Encrypt;
         end if;
      end Encrypt_Char;

   -- Function to decrypt a character
   function Decrypt_Char(Char_To_Decrypt: Character; Shift: Integer) return Character is
      begin
         if Char_To_Decrypt in 'A'..'Z' then
            -- Only decrypt uppercase letters
            return Character'Val((Character'Pos(Char_To_Decrypt) - Shift - Character'Pos('A')) mod 26 + Character'Pos('A'));
         else
            -- Leave other characters unchanged
            return Char_To_Decrypt;
         end if;
      end Decrypt_Char;

   -- Main procedure
   procedure Main is
      Message: String := "HELLO, WORLD!"; -- Example message
      Shift: Integer := 3; -- Shift value (can be any positive integer)

      Encrypted_Message: String(1..Message'Length);
      Decrypted_Message: String(1..Message'Length);
   begin
      -- Encrypt the message
      for I in Message'Range loop
         Encrypted_Message(I) := Encrypt_Char(Message(I), Shift);
      end loop;

      -- Decrypt the encrypted message
      for I in Message'Range loop
         Decrypted_Message(I) := Decrypt_Char(Encrypted_Message(I), Shift);
      end loop;

      -- Display results
      Put_Line("Original Message: " & Message);
      Put_Line("Encrypted Message: " & Encrypted_Message);
      Put_Line("Decrypted Message: " & Decrypted_Message);
   end Main;
begin
   null; -- Empty body
end Caesar_Cipher;

I only had to change null; to Main; to make it work.

3

Thank you.

I just did not have any idea how to fix it without rewriting it from scratch.

I’m not planning on updating the Rosetta Code Task, as I did not contribute to the fix :slight_smile:

What is “Bing copilot”? I’ll google it.

Thanks,
Retired Build Engineer

4

Ah, like ChatGPT or Gemini (Google AI).

5

I’ve created an account to fix that example.

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