An abstract syntax tree (AST) represents program functions and conditions in a hierarchical structure without coding syntax. It helps programmers quickly view code and identify flaws. The tree is abstract because it removes implied symbols, but a concrete syntax tree shows all symbols in detail.
An abstract syntax tree (AST) is a syntactic structure created to represent functions that occur within a program. It is based on the programming source code. Typically hierarchical in design, the abstract syntax tree starts at the core functions and scrolls down to show the most involved functions and code within each core function. Using this tree makes it easier for programmers to view the code without looking through the source code itself, which is much longer and can reveal flaws or weaknesses in the code. The tree is called abstract, not because it’s difficult to understand or has an abstract form, but because it doesn’t include coding syntax such as parenthetical marks and other symbols that inevitably appear in code.
When a programmer creates a program, he must create the functions from things like “if-then” statements and “or else” statements. When looking at the source code, it can be difficult to see if every statement and condition has been fully satisfied and if all functions have been created correctly. An abstract syntax tree gives the programmer a quick way to look at the programming to see each condition and how it applies to the overall program.
The tree is hierarchical. At the top is one of the main statements, and from that statement, branches flow down to show what satisfies the conditions. This continues, showing other features and conditions for the entire program. Variables are also often displayed in programming. Most programming languages have the ability to generate an abstract syntax tree.
Abstract usually means poorly formed, hard to understand, or amorphous. This is not the case with an abstract syntax tree. The reason the word “abstract” is used is because the tree doesn’t show the syntax and programming as-is; rather, it removes implied symbols that aren’t important to the display. For example, parentheses are often used quite liberally in programming, but are not shown in the tree. This is because showing this syntax takes much more space, makes it more difficult to look at the tree, and the programmer would know about these symbols in the source code.
If a programmer wants to see these auxiliary symbols, a concrete syntax tree is often employed. These trees are similar to the abstract variety, only they go into more detail with all the symbols. This tree is better for examining missing parts of symbols or code, while the abstract tree is better for checking program functions and variables.
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