An Interpreter in Object Pascal

Writing an Interpreter in Object Pascal

UPDATE (July 2024): I've been slowly updating and refactoring the code to prepare for writing up the third part of the series. 

UPDATE (9/22/2021): It's a year late but Finally, I have the source code ready for Book 3, it seems stable after much debugging. No memory leaks (based on FastMM) as far as I can tell which is what I've been working on the last two weeks. You can comment out FastMM in the dpr file if you don't need it.  I've committed the code to GitHub together with a debug exe for your convenience if you just want to try it out:

UPDATE (9/16/2020): All the source code for part 1 and 2 of the book series has been moved to GitHub in preparation for part 3: 

Part I - Published

Part II - Published (3/19/2020)

YouTube Playlist which demos some of the functionality of Version 1

Purchase the printed copy that describes the code in detail from Amazon

or as a pdf ebook from Gumroad

The source code, which is open source, can be found at 

Part III

Book for Part 1: How to Purchase

Paperback Copy (with the option to get 50% off the pdf version)  $16.95

Get the eBook (pdf)  $15.95

For more information contact:

This is part 1 of a series that will show you how to write an interactive interpreter in Object Pascal. Part 1 of the series will cover introductory material including a description of the language we’ll create, a full lexical analyzer for the language, how to use DUnitX for unit testing, and an introduction to the essential concepts in syntax analysis, recursive descent, grammar, and EBNF.  Along the way, we’ll create a simple REPL, give a detailed discussion of how to parse expressions and build a simple interactive calculator to illustrate the theory. The book provides fully working code and explains in plain English how the code works and why certain decisions were made, including alternative designs. The book makes liberal use of code throughout the book chapters.   Everything is done without the help of third-party tools such as Yacc, ANTLR or Flex. All you need is a standard installation of Free Pascal or Embarcaderos’s Delphi (including the free community edition).

The text is geared to hobbyists and midlevel developers who need an accessible introduction to lexical analysis and parsing.  It’s also for students starting out in compiler and interpreter design and need something more digestible.

All source code is open source under Apache 2.0 and available from Github.

Available in paperback form from Amazon.

Price $16.95 (paper), $15.95 (eBook) 170 pages

ISBN: 978-1-7325486-0-2


Whats coming up in Part III?