title: IF, THEN, ELSE Integer Constraint Problem
body: <p>I've been stuck on formulating this logical constraint for a while. What I'm trying to translate into an integer constraint is:</p>
  <p>if x1i + x2i + x3i is equal to 3,
  then yi is equal to 1, else yi is equal to 0.</p>
  <p>I found out this kind of works:</p>
  <p>x1i + x2i + x3i &gt;= 3*yi, but in the case where x1i + x2i + x3i is equal to 3, then yi can take on values 0 or 1. I just want it to be strictly one in this case.</p>
  <p>Any insights would be greatly appreciated.</p>