Compilers attribute grammar
What is attribute grammar in compiler?
Attribute grammar is a medium to provide semantics to the context-free grammar and it can help specify the syntax and semantics of a programming language.
Attribute grammar (when viewed as a parse-tree) can pass values or information among the nodes of a tree.
Example: E → E + T { E. value = E..
What is the role of grammar in compiler?
The productions of a grammar specify the manner in which the terminals and non-terminals can be combined to form strings.
Each production consists of a non-terminal called the left side of the production, an arrow, and a sequence of tokens and/or on- terminals, called the right side of the production..
Which attribute is used in compiler?
S-attributed SDT
The S-attributed definition is a type of syntax-directed attributes in compiler design that solely uses synthesized attributes.
The symbol attribute values in the production's body are used to calculate the attribute values for the non-terminal at the head..
Why do we need attribute grammar?
In simple applications, such as evaluation of arithmetic expressions, attribute grammar may be used to describe the entire task to be performed besides parsing in straightforward way; in complicated systems, for instance, when constructing a language translation tool, such as a compiler, it may be used to validate .
- A Programming Language Grammar is a set of instructions about how to write statements that are valid for that programming language.
The instructions are given in the form of rules that specify how characters and words can be put one after the other, to form valid statements (also called sentences). - a word or phrase that is syntactically subordinate to another and serves to limit, identify, particularize, describe, or supplement the meaning of the form with which it is in construction.
In the red house, red is an attribute of house. - S-attributed SDT
The S-attributed definition is a type of syntax-directed attributes in compiler design that solely uses synthesized attributes.
The symbol attribute values in the production's body are used to calculate the attribute values for the non-terminal at the head.Sep 28, 2023
Attribute grammar is a special form of context-free grammar where some additional information (attributes) are appended to one or more of its non-terminals in
Since the size of a grammar determines the size of the parser, attribute grammars enhance compilers with static semantics checking. An attribute grammar is a generative grammar that can describe both the context-free and the context-sensitive syntax of a language.
Type of attribute grammars
ECLR-attributed grammars are a special type of attribute grammars.
L-attributed grammars are a special type of attribute grammars.
They allow the attributes to be evaluated in one depth-first left-to-right traversal of the abstract syntax tree.
As a result, attribute evaluation in L-attributed grammars can be incorporated conveniently in top-down parsing.
LR-attributed grammars are a special type of attribute grammars.
They allow the attributes to be evaluated on LR parsing.
As a result, attribute evaluation in LR-attributed grammars can be incorporated conveniently in bottom-up parsing. zyacc is based on LR-attributed grammars.
They are a subset of the L-attributed grammars, where the attributes can be evaluated in one left-to-right traversal of the abstract syntax tree.
They are a superset of the S-attributed grammars, which allow only synthesized attributes.
In yacc, a common hack is to use global variables to simulate some kind of inherited attributes and thus LR-attribution.
S-attributed grammars are a class of attribute grammars characterized by having no inherited attributes, but only synthesized attributes.
Inherited attributes, which must be passed down from parent nodes to children nodes of the abstract syntax tree during the semantic analysis of the parsing process, are 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.
