The semantics for System F could be explained in roughly a paragraph. Lisp is, more or less, simply typed lambda calculus + code-as-nested-lists + compile-time computation mechanisms; Haskell and ML are System F + various type mechanisms (e.g. typeclasses or modules.)
On the other hand, I suspect an abstract machine for executing Lisp—one that accounted for reader macros and the like—would be of roughly the same complexity as the STG machine.
On the other hand, I suspect an abstract machine for executing Lisp—one that accounted for reader macros and the like—would be of roughly the same complexity as the STG machine.