While writing gcjx, I’ve come to think that our current language
choices are really too weak for a programming task like this. For
most of the work, C++ does just fine, but I’ve run into a couple of
situations where a different approach would be notably better.

First, consider generating synthetic methods. Java compilers have
to do this in a few situations, the most simple one being an implicit
constructor. This involves creating a constructor, setting its return
type and some other attributes, creating a block, adding a
super call to the block, and then adding the block to the
constructor. In all this is about 30 lines of code, which isn’t too
bad in this particular case — but in a lisp-like language, this could
be done much more simply with a single backquoted expression.

Second, suppose you want to add a warning like “warn if
a binary operator on the right hand side of an assignment uses a
narrower type than the assignment itself”. This lets you catch bugs
like double = int / int. In this case, you’d really
like a language that makes tree-matching very easy, say something
with unification.

In both these cases C++ doesn’t fit the bill, and there’s no nice
way that I know of to add the needed syntactic support. I could use
lisp, of course, but then I’m sacrificing static typing. I’m not a
language wonk, though, probably there’s some language out there that
does everything and I just need someone to tell me what it is. Not
that I’ll switch 🙂