Appendix D Text_package package

The text_package package is used by first year students for variable length string 
manipulation. It is loosely based on that provided in the LRM.
Equality can be tested by simply using the standard "=" operator because padding 
is maintained as spaces in the unused portion of the record.
Ada95 allows the overriding of the "=" operator for all types, and allows the 
operands to be of different types, so such padding would not be required.

with text_io;

package text_package is

	max_chars	:constant integer := 256;
	subtype length_range is integer range 0..max_chars;
	subtype index_range is length_range range 
1..length_range'last;


	type text is 
		record
			value	:string(index_range);
			length	:length_range:=0;
		end record;


-------------------------------------------------------------------
-------------
-- read a whole line of characters, throw away anything that 
doesn't fit.

procedure get_line(	item	:in out	text);

procedure get_line(file	:in out	text_io.file_type;
                   item	:in out	text
			);
-------------------------------------------------------------------
-------------
-- put the characters in the_text to the screen. do not include a 
new_line at 
-- the end

procedure put(item	:in	text);

procedure put(file	:in	text_io.file_type;
		item	:in 	text);
-------------------------------------------------------------------
-------------
-- Put the characters in the_text to the screen. Do include a 
new_line at the 
-- end.

procedure put_line(item	:in	text);

procedure put_line(file	:in	text_io.file_type;
			item	:in	text);

-------------------------------------------------------------------
-------------
-- get the string inside the text item.

function to_string(item	:in	text) return string; 


-------------------------------------------------------------------
-------------
-- return the length of the string

function length(item	:in	text) return length_range;


-------------------------------------------------------------------
-------------
-- return true if the string is empty

function empty(item	:in	text) return boolean;


-------------------------------------------------------------------
-------------
-- set the value of "the_text" to "a_string". Disregard any 
characters that
-- don't fit into the record

 function to_text(item	:in	string) return text;


-------------------------------------------------------------------
-------------
-- append a character onto the end of the text
-- disregard anything that doesn't fit in

procedure append(	item   :in out text;
			add_on :in     character);

-------------------------------------------------------------------
-------------
-- append a string onto the end of the text
-- disregard anything that doesn't fit in

procedure append(	item   :in out text;
			add_on :in	 string); 

-------------------------------------------------------------------
-------------
-- append the two text items together 
-- disregard anything that doesn't fit in

procedure append(	item	:in out text;
			add_on :in     text); 

-------------------------------------------------------------------
-------------
-- returns the first n characters of the string, the string is 
padded out with
-- spaces if item is not long enough
--

function first_n_chars(item :in   text;
                       n	  :in   natural) return string;


end text_package;