--------------------------------------------------------------------
--                        a4types.ads                             
-- This file is the specification file for the types 
--    and functions used in the DFA simulation 
--    of Assignment 4.                    
--------------------------------------------------------------------


with TEXT_IO;            use TEXT_IO;

package a4types is

-- These are the record types and access types
-- used by the test program

type terminal is private;
type nonterminal is private;
type rule_ptr is private;
type dfa_ptr is private;
type grammar_ptr is private;


-- These are the procedures and functions used
-- in the test program


-- These functions substitute for constructors, giving
--    a little more control over the initialization, etc.
-- The first function creates an empty grammar.
-- The second and third create representations of
--    rules of a nonregular grammar given a nonterminal 
--    for the left-hand side, a terminal for the right-hand
--    side, and perhaps a nonterminal for the right-hand
--    side.
-- The fourth creates a representation of a DFA given
--    a pointer to a regular grammar.
-- The last two functions convert strings to nonterminals
--    and characters to terminals respectively.

function make_grammar return grammar_ptr;
function make_rule(l:nonterminal; t:terminal) return rule_ptr;
function make_rule(l:nonterminal; t:terminal; r:nonterminal)
     return rule_ptr;
function build_DFA(g:grammar_ptr) return dfa_ptr;
function make_nonterminal(s:string) return nonterminal;
function make_terminal(c:character) return terminal;


-- This is the only mutator used in the test program.
--  It adds a rule to a given grammar.

procedure add_rule(g:grammar_ptr; rr:rule_ptr);


-- And this is the procedure to test a DFA on a given string.
-- Note that it is not a function.

procedure test_string_and_print(d:dfa_ptr; inp:string);


private

-- your type definitions go here
-- (and your other definitions go into an *.adb file)



end a4types;