On Wed, Sep 4, 2013 at 6:32 PM, Daniil Frumin <difrumin@gmail.com> wrote:

I think it's nice that you've raised that question, I will think about
implementing a finer API for calling Haskell from JS.

It sounds like something like h$runSyncWithResult (name open for bikeshedding) that takes an IO (JSRef a) and returns the result to the caller, or null (exception?) when the synchronous thread terminated for some reason, would fit the bill. I think this can be implemented in a few lines of JS.

the current API is a bit bare-bones, based around calling main or a few other top-level IO actions and doing the rest from Haskell code. The Haskell code can make callbacks (JS functions that run Haskell when called, see [1] ), but that can be a bit cumbersome to use when wrapping a library with lots of external JavaScript.

If anyone has ideas of how they'd like a call-Haskell-functions-from-JS API to look, I'd be happy to hear and see if we can make something nice.

One thing to keep in mind though is that type information has been erased from the compiled code, making a generic applyHaskellFun(fun,x,y) that would run 'fun x y' and return its result would be rather risky. That's why the syncCallback/asyncCallback actions use JSRef, letting the Haskell side do the conversion. Going through 'foreign export' could work though, or perhaps there are other options that make this safer.

luite

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