sco1-pylox 0.5.2

A Python interpreter for the Lox programming language.

pylox

Introduction

This is my Python implementation of an interpreter for the Lox programming language from Robert Nystrom's Crafting Interpreters.

Python?

While the text is implemented in Java and C as its high & low-level implementations, I have no idea how to write either of them! Instead, I'll be using Python for the high-level implementation & eventually Rust for the low-level imeplementation.

Differences From Text

For the sake of fitting within a decently sized text, the fully implemented Lox spec omits features that users of other programming languages may miss. Often these are discussed as notes within a chapter, or presented as challenges at the end of a chapter. Significant difference in this implementation from the text reference are noted below.

Defined by Challenges

• (Chapter 4): Arbitrarily nested block comments (/* ... */)
• (Chapter 9): break statements are available for for and while loops

User Choice

• Division by zero returns NaN (Python's float('nan'))
• Strings may be defined using either " or '
• Modulo operator (%)
• Power operator (^)
• Integer division operator (\)
• Both floats and integers are represented
  • Return type from operations follows Python3's semantics
• Containers
  • array()
• A basic include header system
  • Supports "stdlib" imports (<header_name>) and path imports ("path/to/file")
  • Recursive include not supported
  • Imported source assumed to be valid code

Additional Built-ins:

Unless otherwise noted, behavior mirrors the similarly named Python function.

General

• input
• len
• ord
• read_text (via pathlib.Path.read_text)
• str2num
• string_array
  • Gives a LoxArray whose contents are equivalent to collections.deque(<some string>)

Math

• abs
• ceil
• divmod
• floor
• max
• min

Regex

For methods whose Python equivalent returns Match objects, a LoxArray is returned. The first value in the array will always correspond to match.group(0); if the pattern contains one or more groups then the array will match the output of match.groups()

• re_findall
• re_match
• re_search
• re_sub

Stats

• mean
• median
• mode
• std

Pure lox headers

• <array_sum>
• <hello_world>
• <map>
• <split_on>