Oh, I forgot lazy Lisps. But those would probably not be considered "major". > Alternatively, make letrec wrap the values in thunks. Aaaand of course I forgot

Oh, I forgot lazy Lisps. But those would probably not be considered "major". > Alternatively, make letrec wrap the values in thunks. Aaaand of course I forgot that as well. My bad. So basically full lexical scoping and the presence of lambda should be enough to create cyclic structures, even in the absence of mutability.