Book Image

Build Your Own Programming Language

By : Clinton L. Jeffery
Book Image

Build Your Own Programming Language

By: Clinton L. Jeffery

Overview of this book

The need for different types of computer languages is growing rapidly and developers prefer creating domain-specific languages for solving specific application domain problems. Building your own programming language has its advantages. It can be your antidote to the ever-increasing size and complexity of software. In this book, you’ll start with implementing the frontend of a compiler for your language, including a lexical analyzer and parser. The book covers a series of traversals of syntax trees, culminating with code generation for a bytecode virtual machine. Moving ahead, you’ll learn how domain-specific language features are often best represented by operators and functions that are built into the language, rather than library functions. We’ll conclude with how to implement garbage collection, including reference counting and mark-and-sweep garbage collection. Throughout the book, Dr. Jeffery weaves in his experience of building the Unicon programming language to give better context to the concepts where relevant examples are provided in both Unicon and Java so that you can follow the code of your choice of either a very high-level language with advanced features, or a mainstream language. By the end of this book, you’ll be able to build and deploy your own domain-specific languages, capable of compiling and running programs.
Table of Contents (25 chapters)
1
Section 1: Programming Language Frontends
7
Section 2: Syntax Tree Traversals
13
Section 3: Code Generation and Runtime Systems
21
Section 4: Appendix

Counting references to objects

In reference counting, each object keeps a count of how many pointers refer to it. This number starts out as 1 when an object is first allocated and a reference to it is provided to a surrounding expression. The reference count is incremented when the value is stored in a variable, including when the reference is passed as a parameter or stored in a data structure. The count is decremented whenever a reference is overwritten by assigning a variable to refer elsewhere, or when a reference no longer exists (such as when a local variable ceases to exist because a function returns). If the reference count reaches 0, the memory for that object is garbage because nothing points to it. It can be reused for another purpose. This seems pretty reasonable; look at what it would take to add reference counting to our example language in this book, Jzero.

Adding reference counting to Jzero

Jzero allocates two kinds of things from the heap that could be garbage...