title: Hash function for vector<double>
body: <p>First, I am wondering if anyone knows of a hash function for vector representing an n-D vector?</p>
  
  <p>Second, is there a similar hash function where I can specify a resolution such that two "close" vectors hash to the same value?</p>
  
  <p>For example:
  given resolution r = 0.01
  q1 = {1.01, 2.3}
  q2 = {1.01, 2.31} 
  would hash to the same value.</p>
  
  <p>Thanks for the help!</p>