pylox

Complete Python 3.10+ implementation of the Lox programming language from Crafting Interpreters.

You can find some sample code under the example_programs directory.

Some notes:

• Requires python 3.10+ due to the use of pattern matching.
• Type hinting is partially compelete, but mypy doesn't support pattern matching yet so I can't actually run the static checks.

Additional Features:

I've added some additional features where I thought they would be useful. These should not interfere with the base specification of Lox.

1) assert statements

I find these really useful for writing really lazy tests. They work identically to python:

assert <expression>;

This will evaluate the expression and raise an error if it evaluates to something false-y (in Lox, this is only false or nil). It will also print the line number and the actual line of code which includes the assert statement:

For example, in test_scripts/bonus_assertions.lox:

// prints powers of 2 from 2 to 32, then raise an assertion error.
var a = 1;
for (;;){
    a = a * 2;
    print a; 
    assert a != 32;
}

> pylox test_scripts/bonus_assertions.lox
2.0
4.0
8.0
16.0
32.0
Assertion Error on line 5: 
 ->      assert a != 32;

2) Modulo operator (%)

This was provided as an additional exercise in the book.

> pylox
pylox > print 12 % 5;
2.0