[stcredzero]

Squeak is somewhat LightTable-like already, except everything needs to be refreshed manually. (And not all of it is obvious to the beginner, though all of it is readily available if you know how.)

You actually couldn't have everything update automatically and expect bad things never to happen. Functional programming has an advantage here.

[joesb]

Is Light Table written in Haskell-like language? Because other functional language still allow side effect and IO and running everything in those language can still cause bad things.

[stcredzero]

Well, you can have bad things happen even more easily in Smalltalk, but enough of the library is well behaved that it's workable in development, especially since you can save the image periodically and you have a transactional log for even what you do after your last save.

To make Light Table work, you don't need 100% perfect semantics. You just need 99% good semantics, plus some way of turning off automatic refresh and refreshing manually.