Synthesized Attributes

. a syntax directed definition that uses only synthesized attributes is said to be an S- attributed definition

. A parse tree for an S-attributed definition can be annotated by evaluating semantic rules for attributes

S-attributed grammars are a class of attribute grammars, comparable with L-attributed grammars but characterized by having no inherited attributes at all. Inherited attributes, which must be passed down from parent nodes to children nodes of the abstract syntax tree during the semantic analysis, pose a problem for bottom-up parsing because in bottom-up parsing, the parent nodes of the abstract syntax tree are created after creation of all of their children. Attribute evaluation in S-attributed grammars can be incorporated conveniently in both top-down parsing and bottom-up parsing .