Attribute Grammar
Learn about attribute grammar and discuss the commonly used terms in the grammar with a practical example.
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Attribute grammar (AG)
An attribute grammar (AG) is a formalism used in computer science and compiler construction to define the semantics of programming languages. It provides a way to specify and compute attributes associated with the nodes of a syntax tree. These attributes can represent various properties, values, or computations related to the language constructs.
The syntax tree is typically generated during the parsing phase of a compiler, and the attribute grammar is used to associate values with nodes in the tree. This takes place during the subsequent semantic analysis. The attributes can be synthesized or inherited, depending on whether their values are derived from the properties of the node itself, or from its children or other related nodes in the tree.
There are two main types of attributes in attribute grammars, synthesized and inherited attributes. Attribute grammars are often used in the implementation of compilers and programming language processors. They provide a concise and formal way to define the static and dynamic semantics of a programming language. By specifying how attributes are computed and propagated through the syntax tree, attribute grammars facilitate the analysis and transformation of programs. This takes place during the compilation process.
Various tools and systems exist for working with attribute grammars, and they are often employed in the development of programming language implementations and formal language specifications.
Grammar
Attribute grammars are typically described using a formal notation. Let’s consider a simpler example with a grammar for basic arithmetic expressions involving addition and multiplication.
E → E + T | TT → T * F | FF → ( E ) | num
Let’s break down the grammar and examine each production rule in detail.
E → E + T | T:
This production ...