L-attributed grammar

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L-attributed grammars are a special type of attribute grammars.{{cite journal |last1=Knuth |first1=Donald E. |authorlink1=Donald Knuth |date=June 1968 |title=Semantics of context-free languages |journal=Mathematical Systems Theory |volume=2 |issue=2 |pages=127–145 |citeseerx=10.1.1.455.1434 |doi=10.1007/BF01692511 |issn=0025-5661 |s2cid=5182310 |id={{QID|56672530}}}} 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.

A syntax-directed definition is L-attributed if each inherited attribute of $X\_j$ on the right side of $A\; \backslash rightarrow\; X\_1,\; X\_2,\; \backslash dots,\; X\_n$ depends only on

1. the attributes of the symbols $X\_1,\; X\_2,\; \backslash dots,\; X\_\{j-1\}$
2. the inherited attributes of $A$ (but not its synthesized attributes)

Every S-attributed syntax-directed definition is also L-attributed.

Implementing L-attributed definitions in Bottom-Up parsers requires rewriting L-attributed definitions into translation schemes.

Many programming languages are L-attributed. Special types of compilers, the narrow compilers, are based on some form of L-attributed grammar. These are a strict superset of S-attributed grammars. Used for code synthesis.

Either "inherited attributes" or "synthesized attributes" associated with the occurrence of symbol $X\_1,X\_2,\; \backslash dots,\; X\_n$.