In Syntax Directed Translation (SDT), an attribute is called a 'Synthesized Attribute' if its value at a parse tree node N is computed from:
A synthesized attribute at node N is defined solely in terms of the attribute values of the children of N and N itself. It passes information up the parse tree.
An attribute is called an 'Inherited Attribute' if its value at a parse tree node N is computed from:
An inherited attribute is defined from attributes associated with the parent and/or siblings of the node, subject to the dependency rules of the SDD. It is not defined from the attribute instance itself.
Which of the following is TRUE regarding S-attributed and L-attributed Definitions?
S-attributed definitions contain ONLY synthesized attributes. L-attributed definitions allow both synthesized attributes and inherited attributes (restricted to parent and left-siblings). Thus, S-attributed is a strict subset of L-attributed.
In an L-attributed Syntax Directed Definition (SDD), inherited attributes for a symbol $X_{j}$ in production A -> $X_{1}$ $X_{2}$ ... $X_{n}$ can depend on:
In L-attributed definitions, inherited attributes at $X_{j}$ can depend only on inherited/synthesized attributes of the parent A, and attributes of symbols $X_{1}$...$X_{j-1}$ strictly to the left of $X_{j}$.
An S-attributed Grammar can be naturally evaluated during which type of parsing?
Since S-attributed definitions rely purely on synthesized attributes (children to parent), they can be evaluated during bottom-up LR parsing as reductions take place on the parser stack.