Could a Lisp be Blub?
iman: There are languages that have useful features that lisp lacks. For example, Haskell has lazy evaluation and automatic compiler generated program correctness proofs (a decent type system).Then there are languages that try to be even more powerful than Haskell, for example Epigram, which has dependent types.Lazy evaluation is probably the language feature that is most mainstream that lisp lacks. For those not familiar with the abstraction benefits of lazy evaluation, consider a library for dealing with prime numbers. In a language without lazy evaluation, you are going to need an API with a function for getting the n_th prime number, a function for testing if a number is a prime number, a function for getting the smallest prime number larger than the number x, and a bunch of other functions.In Haskell, the API only needs a single variable, called "primes" that is simply the infinite list of all the prime numbers:primes :: [Integer]    -- primes is of type list of IntegerThanks to lazy evaluation, this single variable is all that is needed to support all of the above operations in an efficient way. For example, to get the n_th prime number you simply write (primes !! n)Now, this may look cool, but what does it have to do with abstraction? Since "primes" is a regular list, I can use it with any list function and build more complex things out of it. I can also have a list of all the catalan numbers in the same way, and all my functions that I've written that do cool things with the prime numbers can now be instantly used against catalan numbers.You can manually do lazy evaluation in languages that don't natively have it, but unless you do it everywhere you won't get the abstraction benefits, and if you do do it everywhere then the compiler almost certainly will not be able to optimize it as well as a native implementation.