AST (Abstract Syntax Tree) is a tree-based representation of the abstract syntax of source code. It is a key concept in compiler design, representing the program structure of programming languages without the actual syntactic details (e.g., parentheses and syntactic sugar).
In the parsing phase, the compiler reads the source code, performs lexical analysis to generate tokens, and then these tokens are further analyzed to construct the AST. Each node represents a construct in the program, such as expressions, declarations, or control flow statements.
The AST enables compilers to perform various analysis and optimization tasks, such as type checking, scope resolution, memory allocation, and code generation. Additionally, ASTs are used in static code analysis tools to help developers identify errors in the code or perform complexity analysis.
For example, for the simple mathematical expression 3 + 4 * 5, the AST might have an addition expression as the root node, with two child nodes: the left child is the number 3, and the right child is a multiplication expression with two child nodes, namely 4 and 5.