Amethyst

This is some old stuff, but I haven't blogged about it before so here it goes. Amethyst is basically Perl with Ruby syntax and you can get it here. What it does is parsing Amethyst source (with Ruby-like syntax) using Parse::RecDescent, generating Perl code for the whole program at once (this is a very fragile part), and eval'ing it. Now Ruby and Perl have totally different sematics, so Amethyst hacks around both a lot - for example it can tell whether a Perl object "is" a string, or a number, so + operator acts the expected way on both, even though Perl pretends not to know that. Some examples. Iterators work:

arr = [1,2,3]
arr.each{|element| print(element,"\n")}

The code gets compiled to:

($arr = [1,2,3]);
call(
 method($arr,'each'),
 sub{
   my ($element)=@_;
   {call(function('print'), undef, $element, "\n")}
 },
 $arr
);

And of course prints 1 2 3. The following code prints "22" and "157" as expected:

xs = "15"
xi = xs.to_i

yi = 7
ys = yi.to_s

zi = xi + yi
zs = xs + ys

print(zi, "\n")
print(zs, "\n")

$xs, $xi, $yi, $ys are all native Perl objects, the same you'd get if you said $xs="15"; $yi=7 ; etc. Can you guess how to make a function that can tell them apart without looking inside Amethyst source code ? ;-) Don't expect too much. Unlike RLisp which is basically an usable (even if alpha-quality) programming language, Amethyst was just a single-evening "be evil" session, and half of it was spent learning Parse::RecDescent. Still, it was a lot of fun :-)