https://github.com/mrjameshamilton/loxlox

A Lox interpreter written in Lox
https://github.com/mrjameshamilton/loxlox

interpreter jvm lox lox-language

Last synced: about 5 hours ago
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A Lox interpreter written in Lox

• Host: GitHub
• URL: https://github.com/mrjameshamilton/loxlox
• Owner: mrjameshamilton
• License: mit
• Created: 2023-01-24T22:05:48.000Z (almost 2 years ago)
• Default Branch: main
• Last Pushed: 2024-06-22T16:31:18.000Z (5 months ago)
• Last Synced: 2024-06-22T23:53:43.334Z (5 months ago)
• Topics: interpreter, jvm, lox, lox-language
• Language: Shell
• Homepage:
• Size: 69.3 KB
• Stars: 2
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Lox.lox

A Lox interpreter written in Lox which passes the tests in the Lox test suite.

## Native functions

The following native functions are required to run Lox.lox:

* read(): number

    Returns 1 byte read from standard in.

    Returns `nil` if the end of the stream is reached.

* utf(number, number, number, number): string

    Takes 1, 2, 3, or 4 bytes and returns a corresponding UTF character.

    The Lox function `ascii` is a short-hand for utf(b1, nil, nil, nil).

    Lox supports UTF characters in strings but not other tokens.

* exit(number)

    Exits with the given exit code; used to exit with 65 (error) or 70 (runtime error).

* printerr(string)

    Prints the string to standard error.

These are implemented in a [patch for the original jlox interpreter](https://github.com/mrjameshamilton/loxlox/blob/main/Interpreter.diff), in the [jlox compiler](https://github.com/mrjameshamilton/jlox) and in my implementation of [clox](https://github.com/mrjameshamilton/clox).

## Building

Lox.lox has been tested with the original jlox interpreter, the jlox compiler and clox which are provided as a git submodules, which should be checked out:

```shell

$ git submodule update --init --recursive

```

You'll need Java 20, Dart 2.19 and GCC to build. A build script is provided to patch and build the original jlox interpreter and compile the Lox.lox to a jar with the jlox compiler:

```shell

$ ./build.sh

```

A Lox script can be run with the `bin/loxlox` script which will

pipe the contents of the specified file to the compiled Lox.lox.

```shell

$ echo "print \"Hello World\";" > hello.lox

$ bin/loxlox hello.lox

Hello World

```

The Lox tests can be run by running the `test.sh` script.

```shell

$ ./test.sh

```

## Performance

As a quick performance test, running the below fibonacci example, gives the following run times (on my laptop, approximate average over several runs):

  

    

    jlox interpreter

    jlox compiler

    clox

  

  

    Directly

    1 second

    0.10 seconds

    0.19 seconds

  

  

    Lox.lox

    280 seconds

    18 seconds

    24 seconds

  

```name=fib.lox

fun fib(n) {

  if (n < 2) return n;

  return fib(n - 2) + fib(n - 1);

}

var start = clock();

print fib(30);

var end = clock();

print end - start;

```