You can compile Winxed code with Winxed itself! What’s that you say? The Winxed compiler is bootstrapped and self-hosted, and is written in Winxed and already compiles winxed? Well, that’s all true. Sort of. However there is one small caveat: The Winxed driver program historically has not been able to perform the last step of compilation. The driver compiles winxed code down to PIR, but then uses the spawnw opcode to invoke an instance of Parrot to compile the PIR down to PBC.

I’m pleased to say that this last step is no longer necessary. At least, not in Winxed master (which has not yet been snapshotted into Parrot core).

Here’s a small toy compiler driver that uses Parrot’s PackfileView PMC to compile a .winxed file down into .pbc without spawning any child processes:

function get_winxed_compiler(string pbc_name = "winxedst3.pbc")
    var wx_pbc = load_packfile(pbc_name);
    for (var load_sub in wx_pbc.subs_by_tag("load"))
    return compreg("winxed");

function main[main](var args)
    var wx_compreg = get_winxed_compiler();
    string winxedcc_name = args.shift();
    string infile_name = args.shift();
    string outfile_name = args.shift();

    string code = (new 'FileHandle').readall(infile_name);
    var pf = wx_compreg.compile(code);

That’s less than 20 lines of Winxed code to get the Winxed compiler object loaded, to compile the code and to output the PBC to file. We can make this better, of course, by being more flexible in the handling of arguments and printing out basic help and error messages and all that stuff. Eventually we are going to update the winxed executable itself to use this trick instead of spawning the child process. This should, I hope, have a noticably beneficial effect on compiling with Winxed from the commandline. For large, long builds like Rosella has, any speed improvements are appreciated.

One particularly interesting tidbit to notice is the very first line: A new syntax for handling optional parameters. I put a patch for that feature together last week and NotFound decided he could do the same thing but better than I did. So, the latest Winxed compiler (again, not yet snapshotted into Parrot Core) supports this syntax for providing default values to optional arguments. I hope that this feature is included with the 4.1 release next week. Here are some examples of the new feature in action:

// This...
function foo(var bar [optional], int has_bar [opt_flag])
    if (!has_bar)
        bar = default_bar_value();

// the same as this
function foo(var bar = default_bar_value())

The initializer can be any expression value, including expressions involving previous arguments:

function foo (var bar, var baz = bar.some_method(bar))

This new syntax probably has a few kinks to work out still, but it’s a very cool and very appreciated addition. I’m hoping to use this new syntax to clean up a lot of code in Rosella and hopefully in Jaesop too.