title: When is a boolean function considered "affine"
body: <p>Like the title says my Question is following: When is a boolean function affine? I need this to check if some boolean function(s) make up for an adequat set.</p>
  
  <p>I found following definition: </p>
  
  <blockquote>
    <p>affine if f(x1,...,xn) = c0 ⊕ c1x1 ⊕···⊕ cnxn for some c0,...,cn ∈{0,1}</p>
  </blockquote>
  
  <p>But i don't really get it. Is there some simple way e.g reading it out of a truth table for a small function?</p>
  
  <p>Consider f(x,y) = x ⊕ y</p>
  
  <pre><code>+------------+
  |x  y  |  f  |
  |1  1  |  0  |
  |1  0  |  1  |
  |0  1  |  1  |
  |0  0  |  0  |
  +------------+
  </code></pre>
  
  <p>What does f(x1...xn) mean in this content?</p>
  
  <p>And what is that c0...cn respectively?</p>
  
  <p>Thanks in advance!</p>