Lambda the Ultimate

You can see slides from the Links meeting here and commentary and pictures here. (Thanks to Ethan Aubin for already starting a thread under the former, and to Ehud Lamm for inviting me to guest blog.)

Ethan Aubin writes:

So why do we need a new language? What cannot be accomplished with existing frameworks? There is a slide following this asking why can't you do this in Haskell or ML, but I don't know why they (or even java/php/etc) aren't enough.

Let me try to answer this. Links is aimed at doing certain specific things.

• (a) Generate optimized SQL and XQuery directly from the source code -- you don't need to learn another language, or work out how to partition your program across the three tiers. This idea is stolen from Kleisli. You need to build it into the compiler, so Haskell, Ocaml, or PLT Scheme won't do.
• (b) Generate Javascript to run in the browser directly from the source code -- you don't need to learn another language, or work out how to partition your program across the three tiers. We're hoping to provide a better way to write AJAX style programs. Again, you need compiler support -- vanilla Haskell, Ocaml, or PLT Scheme can't do this.
• (c) Generate scalable web interfaces -- where scalable means all state is kept in the client (in hidden fields), not in the server. PLT Scheme and WASH provide the right interface, but they are not scalable in this sense, precisely because making them scalable involves fiddling with the compiler. (Felleisen and company have pointed out the right way to do this, applying the well-known CPS and defunctionalization transformations.)

So that's my argument for a new language.

Is it a good enough argument? Is this enough of an advantage to get folk to move from PHP, Perl, Python? Not clear. I suspect if it is good enough, a major motivating factor is not going to be anything deep, but simply the fact that being able to write everything down in one language instead of three or four will make people's brains hurt less.

Ethan Aubin also writes:

Wadler goes into the FP success stories, Kleisli, Xduce, PLT Scheme (Continuations on the Web), Erlang. If you take the befenits of these individually, you've got a language which solves the 3-tier problem better than what we have now, but I don't think it meet the criteria of "permitting its users to do something that cannot be done in any other way". So, I'd like to ask the all the perl/php/asp/pythonistas on LtU, what it is the killer-app that that your language cannot handle?

I'd love to see answers to this question!