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:
“Virtue, my pet, is an abstract idea, varying in its manifestations with the surroundings. Virtue in Provence, in Constantinople, in London, and in Paris bears very different fruit, but is none the less virtue.”
—Honoré De Balzac (1799–1850)
“And out of the ground made the Lord God to grow every tree that is pleasant to the sight, and good for food: the tree of life also in the midst of the garden, and the tree of knowledge of good and evil. And a river went out of Eden to water the garden.”
—Bible: Hebrew Genesis 2:9-10.