Wiki Overview — Interpreters: PLAI, Tolk, Advprog

This wiki covers the theory and practice of writing interpreters for programming languages, as taught in the Advanced Programming (Advprog) course and grounded in the textbook Programming Languages: Application and Interpretation (PLAI, 2nd ed.) by Shriram Krishnamurthi. The implementation language is Common Lisp, using the tolk library. Currently: 7 sources, ~20 pages, 4 clusters.

interpreter-architecture  ← core theory: AST, parse, interpret, semantics
       │
       ├── tolk-implementation  ← CL realisation of the theory
       │
       ├── plai-book            ← source text (chs. 1-3 so far)
       │
       └── advprog-course       ← classroom application

Enter at: Interpreter Architecture

The central cluster. Covers the design of the parse→interpret pipeline, abstract syntax trees, the role of semantics, and how meaning is assigned to language constructs. All other clusters connect to this one.

Key entry points:

• "What is an AST?" → Abstract Syntax Tree
• "How does parsing work?" → Parsing
• "How does an interpreter evaluate?" → Interpreter

Enter at: Tolk

The Common Lisp realisation of PLAI's interpreter patterns. Uses CLOS for AST nodes, trivia for pattern matching, metabang-bind for slot binding, and fiveam for tests. The arithmetic interpreter (tolk/arith) is the first language implemented.

Key entry points:

• "How does tolk represent AST nodes?" → Abstract Syntax Tree
• "How does tolk's arith interpreter work?" → Tolk Arith

Enter at: PLAI

Shriram Krishnamurthi's textbook. Chapters 1-3 are ingested. The book uses plai-typed (a typed Racket dialect); tolk/advprog uses Common Lisp instead.

Enter at: Advprog

The Advanced Programming course at AUC. Interpreter material begins with the 2026-04-20 class. Follows PLAI loosely; uses Common Lisp throughout.