-- Example of function types and variables
-- in Ada on page 211 of
-- Kenneth C. Louden, Programming Languages
-- Principles and Practice 2nd Edition
-- Copyright (C) Brooks-Cole/ITP, 2003

with Text_IO; use Text_IO;
with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;

procedure functype is

  type IntFunction is 
          access function (x:integer) return integer;
  -- "access" means pointer in Ada

  function square (x: integer) return integer is
  begin
    return x * x;
  end square;

  function evaluate (g: IntFunction; value: integer) 
      return integer is
  begin
    return g(value);
  end evaluate;

  f: IntFunction := square'access; 
     -- note use of access attribute to get pointer to square

begin
  put(evaluate(f,3)); -- evaluates to 9
  new_line;
end;