/*  Provides methods to evaluate a variety of
    kinds of assertions.
    B. Sanders,  July 1997.

    If boolean expression is false, program will throw an
    AssertionException, aborting in the default case.
    The versions with string parameters will print the string
    when aborting program.

    If the boolean expression is true, program execution 
    continues.

    To use this class:  
     1.  Save this source in a file called Assertions.java in your
          working directory
     2. Compile (javac Assertsion.java)
     3. Your program may then contain commands such as
           Assertions.assert(x>0);
           Assertions.inputCheck(-100 <= x <= 100);
        etc.  
*/


class Assertions
{

  public static void assert(boolean Q)
  {
    assert(Q,"Assertion Error");
  }

  public static void assert(boolean Q, String s)
  {
    if (!Q)  
    { 
       throw new AssertionException(s);
    }
    else return;
  }


  public static void inputCheck(boolean Q)
  {  assert(Q,"Input Error");
  }

  public static void inputCheck(boolean Q, String s)
  {  assert(Q,"Input Error: " + s);
  }

  public static void precondition(boolean Q)
  {  assert(Q, "Precondition violated");
  }

  public static void precondition(boolean Q, String s)
  { assert(Q, "Precondition violated: " + s);
  }


  public static void main(String[] args)
  { System.out.print("Enter true or false: "); 
    System.out.flush();
    boolean b = Input.readBoolean();
    assert(b);
    System.out.print("Enter true or false, and a word: "); 
    System.out.flush();
    b = Input.readBoolean();
    String s = Input.readString();
    assert(b,s);
  }

}

class AssertionException extends RuntimeException
{
   AssertionException(String s)
  { super(s);
  }
}