Writing A Compiler In Go is the sequel to Writing An Interpreter In Go. It starts right where the first one stopped, with a fully-working, fully-tested Monkey interpreter in hand, connecting both books seamlessly, ready to build a compiler and a virtual machine for Monkey. In this book, we use the codebase (included in the book!) from the first part and extend it. We take the lexer, the parser, the AST, the REPL and the object system and use them to build a new, faster implementation of Monkey, right next to the tree-walking evaluator we built in the first book. The approach is unchanged, too. Working, tested code is the focus, we build everything from scratch, do baby steps, write tests firsts, use no 3rd-party-libraries and see and understand how all the pieces fit together. It's a continuation in prose and in code.