Longest common prefix: Difference between revisions

=={{header|Ada}}==

<lang Ada>with Ada.Text_IO;

with Ada.Strings.Unbounded;

procedure Longest_Prefix is

package Common_Prefix is

procedure Reset;

procedure Consider (Item : in String);

function Prefix return String;

end Common_Prefix;

package body Common_Prefix

is

use Ada.Strings.Unbounded;

Common : Unbounded_String;

Active : Boolean := False;

procedure Reset is

begin

Common := Null_Unbounded_String;

Active := False;

end Reset;

procedure Consider (Item : in String) is

Len : constant Natural := Natural'Min (Length (Common), Item'Length);

begin

if not Active then

Active := True;

Common := To_Unbounded_String (Item);

else

for I in 1 .. Len loop

if Element (Common, I) /= Item (Item'First + I - 1) then

Head (Common, I - 1);

exit;

end if;

end loop;

end if;

Head (Common, Len);

end Consider;

function Prefix return String is (To_String (Common));

end Common_Prefix;

use Common_Prefix;

begin

Consider ("interspecies"); Consider ("interstellar"); Consider ("interstate");

Ada.Text_IO.Put_Line (Prefix);

Reset; Consider ("throne"); Consider ("throne");

Ada.Text_IO.Put_Line (Prefix);

Reset; Consider ("throne"); Consider ("dungeon");

Ada.Text_IO.Put_Line (Prefix);

Reset; Consider ("prefix"); Consider ("suffix");

Ada.Text_IO.Put_Line (Prefix);

Reset; Consider ("foo"); Consider ("foobar");

Ada.Text_IO.Put_Line (Prefix);

Reset; Consider ("foo");

Ada.Text_IO.Put_Line (Prefix);

Reset; Consider ("");

Ada.Text_IO.Put_Line (Prefix);

Reset;

Ada.Text_IO.Put_Line (Prefix);

end Longest_Prefix;</lang>