. In case of both inherited and synthesized attributes

. An inherited attribute for a symbol on rhs of a production must be computed in an action before that symbol

S A 1 A 2	{A 1 .in = 1,A 2 .in = 2}
A a	{print(A.in)}

depth first order traversal gives error undefined

. A synthesized attribute for non terminal on the lhs can be computed after all attributes it references, have been computed. The action normally should be placed at the end of rhs

We have a problem when we have both synthesized as well as inherited attributes. For the given example, if we place the actions as shown, we cannot evaluate it. This is because, when doing a depth first traversal, we cannot print anything for A1. This is because A1 has not yet been initialized. We, therefore have to find the correct places for the actions. This can be that the inherited attribute of A must be calculated on its left. This can be seen logically from the definition of L-attribute definition, which says that when we reach a node, then everything on its left must have been computed. If we do this, we will always have the attribute evaluated at the correct place. For such specific cases (like the given example) calculating anywhere on the left will work, but generally it must be calculated immediately at the left.