Syntaxträds

Syntaxträds, commonly referred to in English as syntax trees or parse trees, are graphical representations of the syntactic structure of sentences or source code according to a formal grammar. In linguistics, a syntax tree expresses constituency: internal nodes denote syntactic categories (such as S, NP, VP, PP) and leaves correspond to the sequence of words. The root represents the whole sentence, and the yield is the linear string formed by the leaves. Dependency trees, which encode grammatical relations as head–dependent links, offer an alternative view of structure.

In programming languages, a similar concept appears as parse trees or abstract syntax trees (ASTs). A parse tree reflects the exact concrete syntax produced by a parser, including punctuation and boilerplate tokens. An AST, by contrast, removes much of the concrete syntax to highlight the semantic structure of the program, with nodes representing constructs such as declarations, expressions, statements, and operators. ASTs are commonly used in later stages of compilation or interpretation, including semantic analysis, optimization, and code generation.

Construction and methods: Trees are generated by parsers that follow a grammar, often context-free grammars for natural or programming languages. Parsing techniques include top-down and bottom-up approaches, LL and LR parsers, and chart or CYK algorithms. After parsing, a tree may be transformed into an AST to suit subsequent processing.

Applications: In linguistics, syntax trees support analysis, theory testing, and computational language processing. In computer science, they are central to compilers and interpreters, enabling syntax checking, translation, and optimization, as well as to various natural language processing tasks such as parsing and semantic interpretation.

Notes: The term syntaxträds can refer to both constituency trees in linguistics and parse or abstract syntax trees in computing, with terminology varying by field.