Pylox

An implementation of a tree walker interpreter for the Lox language from the book Crafting Interpreters by Bob Nystrom in Python. The interpreter can be used in two different modes:

1. REPL - statements & expressions are passed through the terminal. statements are executed while expressions are evaluated and displayed.
2. Passing a file as a command line argument.

Challenges completed:

Chapter 6 - Parsing Expressions:

• Added the Comma operator.
• Added the Ternary Operator.
• Error reporting on binary operators missing a left-hand operand.

Chapter 7 - Evaluating Expressions:

• Added comparison operators to strings, chose not to allow comparison between mixed types.
• Added support for concatenating strings and numbers.
• Error report for division by zero.

Chapter 8 - Statements And State:

• REPL now works in the following way: statements are executed, while expressions are evaluted and displayed.
• Accessing an undefined variable is now a runtime error.

Chapter 9 - Control Flow:

• Added support for a break statement.

Chapter 10 - Functions:

• Lambda functions are now supported.

Chapter 11 - Resolving And Binding:

• An unused & defined variable now raises a runtime error.
• Changed implementation of an environment to a list instead of a dictionary.

Chapter 12 - Classes:

• Added metaclasses, and through them added support for class methods.
• Added support for get methods - more info here.

Personal Additions To The Lox Native Library\LNL

• Added a native input command - read(message) - message will be printed as a prompt for the user.

• Added a native array class which has the following methods:

  set(i, value) - if i is not nil then set value at index i, otherwise append value to the end.

  get(i) - returns the value at index i.

  length() - returns the length of the array.

• Changed print to be a native function.