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  31 
  32 // Simple sample demonstrating "fixed point" computation with Streams
  33 
  34 // See also https://mitpress.mit.edu/sicp/chapter1/node21.html#secprocgeneralmethods
  35 var Stream = Java.type("java.util.stream.Stream");
  36 
  37 // generic fixed point procedure
  38 function fixed_point(f, init_guess) {
  39   var tolerance = 0.00001;
  40   function close_enough(v1, v2) Math.abs(v1 - v2) < tolerance;
  41  
  42   var prev; 
  43   return Stream.iterate(init_guess, f)
  44       .filter(function(x) {
  45           try {
  46               return prev == undefined? false : close_enough(prev, x);
  47           } finally {
  48               prev = x;
  49           }
  50       })
  51       .findFirst()
  52       .get();
  53 }
  54 
  55 // solution to x = cos(x)
  56 print(fixed_point(Math.cos, 1.0))
  57 
  58 // solution to x = sin(x) + cos(x)
  59 print(fixed_point(function(x) Math.sin(x) + Math.cos(x), 1.0));
  60 
  61 // square root by Newton's method
  62 // http://en.wikipedia.org/wiki/Newton's_method
  63 function sqrt(n)
  64   fixed_point(function(x) (x + n/x) / 2, 2.0);
  65 
  66 print(sqrt(2))
  67 print(sqrt(3))
  68 
  69