Load File: __quadrature.sml

   This module performs automatic quadrature using Simpson's rule.  It
   illustrates the use of the Real structure in the basis library.
   The module provides two functions, Quadrature.integrate and 
   Quadrature.differentiate.

   The function Quadrature.integrate takes arguments f, a, b, and accuracy and
   integrates the function f between limits a and b to accuracy specified.  
   If accuracy is NONE then maximum accuracy will be used.  If either of 
   the limits is infinity or NaN, then the exceptions Overflow or Div will 
   be raised respectively.  If any value in the integral cannot be evaluated 
   then the exception Eval will be raised for that point.  (These precautions 
   stop the calculation going into an infinite loop.)

   For example:

       Quadrature.integrate((fn x => 1.0 / x),1.0, 2.0,NONE);

   gives

       val it : real = 0.6931471806

   and

       Quadrature.differentiate (fn x => 1.0 / x) 3.0;
 
   gives
 
       val it : real = ~0.1111111082


   This module is also used to calculate probabilities in the Normal 
   distribution demo module.