AST Node Structures

ASTs Represent Syntax Trees

The parser's output is an abstract syntax tree: a tree of nodes for expressions, statements, and declarations. Clang builds Expr and Stmt subclasses; LLVM's frontend lowers from similar structures. Every semantic check and code generator walks this tree.

Node Design

Each AST node has a type tag, source location, and child pointers. Expression nodes cover literals, identifiers, binary/unary ops, and calls. Statement nodes cover assignments, if/while, return, and blocks. Keep the hierarchy shallow enough to traverse easily.

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• Literals store numeric or string values
• Binary nodes store operator and two children
• If nodes store condition, then-branch, else-branch
• Locations enable error messages in later phases

Connecting to real compilers

Production compilers embed this step inside a longer pipeline. GCC flows through cpp, cc1, assembly, and ld; Clang uses the driver, Sema, LLVM IR passes, and a target backend. LLVM bitcode, JVM bytecode, and WASM are other familiar IRs at the same layer. The exercise isolates one pass so you can test it alone before chaining it to the next stage.

Why for this exercise

You will define AST node types and structures for expressions and statements. This exercise asks you to model the parse tree data layout that your parser builds and that semantic analysis traverses.