with Text_io;
procedure BINSRCH is --{by RJBotting, (C) Jan 1992}
 
    max_index:constant:=80;
 
    NOT_FOUND:exception; --when search fails to find item
    subtype ITEM is character;
    subtype INDEX is integer range 1..max_index;
    type LIST is array (INDEX) of ITEM;
 
    type SUBLIST is array(INDEX range <>) of ITEM;
		--Binary search works by extracting sublists
 
    package Index_io is new text_io.Integer_IO(NUM=>INDEX);
 
    L:LIST:=(1..max_index=>ASCII.DEL);
    SIZE:INDEX;
 
    procedure GET_LIST(L:out LIST; size:out index) is
    begin
        for I in INDEX loop
            Text_io.get(L(I));
	    if text_io.end_of_line then
		size:=I;
		return;
	    end if;
        end loop;
    end GET_LIST;
 
    procedure WRITELIST(L:in SUBLIST) is
    begin
        for I in L'range loop
            Text_io.Put(L(I));
        end loop;
    end WRITELIST;
 
    function SEARCH(The_table:SUBLIST; TARGET:ITEM) return integer is
    begin
	text_io.put("DEBUG:");writelist(The_Table);text_io.new_line;
	if the_table'length<=1 then
		if the_table(the_table'first)= Target then 
			return The_table'first;
		else 	raise not_FOUND;
		end if;
	else
  	  declare MID:INDEX:=(the_table'First+The_Table'LAST)/2;
	  begin
		if the_table(mid)>Target then
		    return search(The_table(the_table'first..Mid-1), Target);
		elsif the_table(mid)<target then
		    return Search(The_table(Mid+1..The_table'last), Target);
		else return mid;
		end if;
	  end;
 
	end if;
    end SEARCH;
 
begin
    Text_io.Put("Input upto ");
    Text_io.Put(integer'image(MAX_INDEX));
    Text_io.Put_line(" characters in Alphabetic order and tap Enter...");
    Get_list(L, size);
    declare
	S:SUBLIST(1..SIZE):=SUBLIST(L(1..SIZE));
	TARGET:character;
    begin
    	WRITELIST(S);
	text_io.new_line;
	Text_IO.put("Input character to search for> ");
	Text_IO.GET(Target);
 
	text_io.new_line;
	Index_io.put(search(S,  Item(Target) ) );
	text_io.new_line;
    exception
	when not_found=>text_IO.put("Target not in list"); text_io.new_line;
 	when others=>raise;
    end;
end;