title: What node I can I optimise by tree reduction in bison?
body: <p>If I make a compiler where the output of bison is a tree.  I want to optimise that tree by reducing the tree for constant expressions. For example,
  if I have an <code>(if_else_node)</code> I can reduce this node by checking <code>(expression_if == true)</code> then I don't need to visit the <code>(else_node)</code>.</p>
  
  <p>Another example of reduction:</p>
  
  <p>If I have an <code>(add_node)</code> and I have the expression  <code>(7+9+2+6)</code> I can reduce this to <code>(add_node) (18 + 6)</code>.</p>
  
  <p>My question is what another nodes can I reduce in the bison tree?</p>