Correct : b,d

• a) An attribute grammar is an SDD with no side effects:
  By formal definition, an attribute grammar is a Syntax-Directed Definition (SDD) that uses semantic functions without any side effects (such as directly printing values or updating global tables). It strictly computes values of attributes from other attributes.
  → This statement is TRUE.


• b) The attributes in an L-attributed definition cannot always be evaluated in a depth-first order:
  L-attributed definitions are explicitly structured to allow attribute evaluation via a natural depth-first, left-to-right traversal. Because dependency graphs for L-attributed definitions are guaranteed to have no cycles, they can always be evaluated in a depth-first sequence.
  → This statement is FALSE.


• c) Synthesized attributes can be evaluated by a bottom-up parser as the input is parsed:
  A bottom-up parser (like an LR parser) naturally reduces children nodes into parent nodes. Since a synthesized attribute computes its value based on the values of its children nodes, its evaluation perfectly aligns with the shift-reduce actions of a bottom-up parser.
  → This statement is TRUE.


• d) All L-attributed definitions based on an LR(1) grammar can be evaluated using a bottom-up parsing strategy:
  While L-attributed definitions can always be evaluated during top-down parsing, they cannot all be evaluated during a single-pass bottom-up parsing run. For a bottom-up parser to evaluate an inherited attribute, the value must be available before the parent or siblings are fully reduced, which often requires introducing marker non-terminals. If these markers break the underlying LR(1) nature of the grammar, a single-pass bottom-up evaluation becomes impossible.
  → This statement is FALSE.