README

PLOX

Plox is an inplementation of the Lox language in PHP.

How to try it

# run a Lox script
$ php plox.php hello.lox
# or after 'chmod +x plox'
$ ./plox hello.lox

If you want to try the Lox syntax, you can also launch the interpreter without a filename to have a REPL prompt (you have to write all the code on one line):

$ ./plox
> var test = 3; print test;
3
>

Improvements

I've added a few things that the book does not cover.

Constants collapsing

If a binary operator is used with two constants, then a new constant node is created instead of the binary operator node.

1 + 1 creates LiteralExpr(2) instead of BinaryExpr(LiteralExpr(1), '+', LiteralExpr(1)).

Warnings

I've added a couple of warnings about variables being declared to soon or being unused.

var a = 3;
var b = 4;
{
	print(a); // WARNING: variable 'a' declared on line 1 is only used in an inner scope.
}
// WARNING: variable 'b' declared on line 2 is never used.

TODO: add 'read uninitialised variable' and 'variable never read'

Plox