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

Finding redeclared variables

When a variable has been declared, most languages report an error if the same variable is declared again in the same scope. The reason for this is that within a given scope, the name must have a single, well-defined meaning. Trying to declare a new variable would entail allocating some new memory and from then on, mentioning that name would be ambiguous. If the x variable is defined twice, it is unclear which x any given use refers to. You can identify such redeclared variable errors when you insert symbols into the symbol table.

Inserting symbols into the symbol table

The insert() method in the symbol table class calls the language's underlying hash table API. The method takes a symbol, a Boolean isConst flag, and an optional nested symbol table, for symbols that introduce a new (sub)scope. The Unicon implementation of the symbol table's insert() method is shown here. If you go to https://github.com/PacktPublishing/Build-Your-Own-Programming...