Lox解释器的Swift实现版本

Lox是一门迷你编程语言，来自于Bob Nystrom写的编译器教程Crafting Interpreters

UPDATE 2022/05/27 已经完成本书PART II

会尽量参照书中PART II所示的Java代码结构来实现

但是Swift本身有太多优秀和新奇的特点，比如enum、Optional、POP等，我也会使用这些Swift独占特性，但整体的结构和逻辑应该和书本上的并无太大差异

• 4. Scanning

  • Challenge 4: C-style /* ... */ block comments.

• 5. Representing Code

  • Challenge 3: AST Printer In Reverse Polish Notation.
  • GenerateAst tool

• 6. Parsing Expressions

  • Challenge 1: Add prefix and postfix ++ and -- operators.
  • Challenge 2: Add support for the C-style conditional or “ternary” operator ?:
  • Challenge 3: Add error productions to handle each binary operator appearing without a left-hand operand.

• 7. Evaluating Expressions

  • Challenge 1: Allowing comparisons on types other than numbers could be useful.
  • Challenge 2: Many languages define + such that if either operand is a string, the other is converted to a string and the results are then concatenated.
  • Challenge 3: Change the implementation in visitBinary() to detect and report a runtime error when dividing by 0.

• 8. Statements and State

  • Challenge 1: Add support to the REPL to let users type in both statements and expressions.
  • Challenge 2: Make it a runtime error to access a variable that has not been initialized or assigned to

• 9. Control Flow

  • Challenge 3: Add support for break statements.

• 10. Functions

  • Challenge 2: Add anonymous function (lambdas) syntax.

• 11. Resolving and Binding

  • Challenge 3: Extend the resolver to report an error if a local variable is never used.
  • Challenge 4: Store local variables in an array and look them up by index.

• 12. Classes

  • Challenge 1: Add class methods.
  • Challenge 2: Support getter methods.

• 13. Inheritance

  • Challenge 1: Multiple inheritance. Nothing to implement...?
  • Challenge 2: Reverse method lookup order in class hierarchy.

我尽量使用TDD的**来开发每个阶段，所以Xcode工程中包含了使用XCTest实现的单元测试文件。

使用 SPM 来管理frameworks、依赖文件

解释器的主体实现包含在一个framework中，通过一个简单的CLI程序使用该framework来运行解释器

• slox: 可执行文件，用于在CLI中直接运行解释器
• LoxCore: 包含Lox核心实现的Swift framework