In computer science, an abstract syntax tree (AST), or just syntax tree, is a tree representation of the abstract syntactic structure of source code written in a programming language. Each node of the tree denotes a construct occurring in the source code. The syntax is 'abstract' in the sense that it does not represent every detail that appears in the real syntax. For instance, grouping parentheses are implicit in the tree structure, and a syntactic construct such as an if-condition-then expression may be denoted by a single node with two branches.
This makes abstract syntax trees different from concrete syntax trees, traditionally called parse trees, which are often built by a parser as part of the source code translation and compiling process. Once built, additional information is added to the AST by subsequent processing, e.g., contextual analysis.
Abstract syntax trees are also used in program analysis and program transformation systems.
Famous quotes containing the words abstract and/or tree:
“What persuades men and women to mistake each other from time to time for gods or vermin is ideology. One can understand well enough how human beings may struggle and murder for good material reasons—reasons connected, for instance, with their physical survival. It is much harder to grasp how they may come to do so in the name of something as apparently abstract as ideas. Yet ideas are what men and women live by, and will occasionally die for.”
—Terry Eagleton (b. 1943)
“If the tree is straight it need not fear casting a crooked shadow.”
—Chinese proverb.