While I'm a big fan of immutable design, it makes some algorithms much more expensive and ultimately DRAM is mutable. And the example we're talking about could be a loop counter!

A tail-recursive loop handles loops just fine, and is just as efficient. This is a perfect example of the misconceptions that mutable-first programming languages have caused.

> ultimately DRAM is mutable

Ultimately the CPU executes machine code, but I don’t see you directly writing that. You’re cherry-picking to defend an indefensible position.

Yes! In lazy but immutable languages like Haskell, it is totally fine to refer to the value itself during definition. This is really the same idea that a recursive function can refer to itself during definition. It’s common to define a variable for the infinite list of prime numbers, where the definition requires the list of prime numbers itself.

    primes = 2 : sieve primes [3..]
    sieve (p:ps) xs = let (h, t) = span (< p*p) xs in h ++ sieve ps (filter (\n -> rem n p > 0) t)

Here `primes` is a variable that refers to itself in its definition (called corecursion), and `sieve` is a recursive function.