From what I saw, the Ogone official extension offers this feature: http://www.magentocommerce.com/magento-connect/ogone-9913.html. if you install it take a look through the config settings.

Which built-in payment methods in Magento (or extensions) offer an iframe option?
I'm trying to find how call/cc is implemented. The best I've found is this Haskell snippet:

callCC f = Cont $ \k -&gt; runCont (f (\a -&gt; Cont $ \_ -&gt; k a)) k


Although this is not as simple as I want due to the Cont and runCont. I've also found descriptions of what it does, although never as clear as actual code.

So how is it implemented in its simplest form? I am tagging this with Scheme and Haskell as those are two languages I prefer.
