Concrete Syntax Trees

Concrete Syntax Trees (CST) are a detailed representation of source code that captures every syntactic element, including tokens, whitespace, and punctuation, as they appear in the original text. They are generated during the parsing phase of compilation or interpretation and serve as an intermediate structure between raw code and more abstract representations like Abstract Syntax Trees (AST). CSTs preserve the exact syntax of the source, making them useful for tasks that require precise formatting or error reporting.

Also known as: Parse Trees, Syntax Trees, CST, Concrete Parse Trees, Full Syntax Trees

Why learn Concrete Syntax Trees?

Developers should learn about Concrete Syntax Trees when working on compilers, interpreters, linters, code formatters, or syntax highlighting tools, as they provide a complete view of the source code's structure. They are essential for applications that need to reconstruct or manipulate code exactly as written, such as in refactoring tools or when generating code from templates, because they retain all syntactic details that ASTs abstract away.

Learning Resources

• docs: Wikipedia: Parse Tree
• book: Crafting Interpreters: Representing Code
• tutorial: GeeksforGeeks: Parse Tree and Syntax Tree
• video: YouTube: Concrete vs Abstract Syntax Trees
• tutorial: Compiler Design: Syntax Analysis