Ada Programming/Algorithms/Chapter 1

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Ada. Time-tested, safe and secure.
Ada. Time-tested, safe and secure.

Chapter 1: Introduction[edit | edit source]

The following subprograms are implementations of the Inventing an Algorithm examples.

To Lower[edit | edit source]

The Ada example code does not append to the array as the algorithms. Instead we create an empty array of the desired length and then replace the characters inside.

File: to_lower_1.adb (view, plain text, download page, browse all)
  function To_Lower (C : Character) return Character renames

  --  tolower - translates all alphabetic, uppercase characters
  --  in str to lowercase
  function To_Lower (Str : String) return String is
     Result : String (Str'Range);
     for C in  Str'Range loop
        Result (C) := To_Lower (Str (C));
     end loop;
     return Result;
  end To_Lower;

Would the append approach be impossible with Ada? No, but it would be significantly more complex and slower.

Equal Ignore Case[edit | edit source]

File: to_lower_2.adb (view, plain text, download page, browse all)
  --  equal-ignore-case -- returns true if s or t are equal,
  --  ignoring case
  function Equal_Ignore_Case
    (S    : String;
     T    : String)
     return Boolean
     O : constant Integer := S'First - T'First;
     if T'Length /= S'Length then
        return False;  --  if they aren't the same length, they
                       --  aren't equal
        for I in  S'Range loop
           if To_Lower (S (I)) /=
              To_Lower (T (I + O))
              return False;
           end if;
        end loop;
     end if;
     return True;
  end Equal_Ignore_Case;