Blog

Parsers and ASTs: Recursive Descent, Operator Precedence and Pratt Parsing

A parser turns tokens into a single AST following precedence and associativity rules; Pratt parsing keeps those rules in a binding power table instead of a chain of methods. For the Bookstore filter language we derive a recursive descent parser from the grammar, write the same language with a Pratt parser and test that both build the same tree, report several errors at once with panic mode, and run the AST with a tree-walking interpreter.