Writing an Interpreter in Go

 Acknowledgments....5 Introduction....6 The Monkey Programming Language & Interpreter....7 Why Go?....9 How to Use this Book....10 Lexing....11 1.1 - Lexical Analysis....11 1.2 - Defining Our Tokens....12 1.3 - The Lexer....14 1.4 - Extending our Token Set and Lexer....22 1.5 - Start of a REPL....27 Parsing....30 2.1 - Parsers....30 2.2 - Why not a parser generator?....32 2.3 - Writing a Parser for the Monkey Programming Language....33 2.4 - Parser's first steps: parsing let statements....34 2.5 - Parsing Return Statements....46 2.6 - Parsing Expressions....48 Expressions in Monkey....49 Top Down Operator Precedence (or: Pratt Parsing)....50 Terminology....50 Preparing the AST....51 Implementing the Pratt Parser....54 Identifiers....55 Integer Literals....58 Prefix Operators....61 Infix Operators....65 2.7 - How Pratt Parsing Works....71 2.8 - Extending the Parser....79 Boolean Literals....81 Grouped Expressions....84 If Expressions....86 Function Literals....91 Call Expressions....95 Removing TODOs....99 2.9 - Read-Parse-Print-Loop....102 Evaluation....105 3.1 - Giving Meaning to Symbols....105 3.2 - Strategies of Evaluation....106 3.3 - A Tree-Walking Interpreter....107 3.4 - Representing Objects....108 Foundation of our Object System....110 Integers....110 Booleans....111 Null....111 3.5 - Evaluating Expressions....112 Integer Literals....113 Completing the REPL....115 Boolean Literals....116 Null....118 Prefix Expressions....118 Infix Expressions....122 3.6 - Conditionals....127 3.7 - Return Statements....129 3.8 - Abort! Abort! There's been a mistake!, or: Error Handling....133 3.9 - Bindings & The Environment....138 3.10 - Functions & Function Calls....142 3.11 - Who's taking the trash out?....152 Extending the Interpreter....154 4.1 - Data Types & Functions....154 4.2 - Strings....154 Supporting Strings in our Lexer....155 Parsing Strings....157 Evaluating Strings....158 String Concatenation....160 4.3 - Built-in Functions....162 len....162 4.4 - Array....166 Supporting Arrays in our Lexer....167 Parsing Array Literals....168 Parsing Index Operator Expressions....171 Evaluating Array Literals....174 Evaluating Index Operator Expressions....176 Adding Built-in Functions for Arrays....179 Test-Driving Arrays....182 4.5 - Hashes....183 Lexing Hash Literals....184 Parsing Hash Literals....186 Hashing Objects....190 Evaluating Hash Literals....194 Evaluating Index Expressions With Hashes....197 4.6 - The Grand Finale....200 Resources....202 Feedback....204 Changelog....205