why memoization is not a language feature?

Question

I was wondering... why memoization is not provided natively as a language feature by any language I know about?

Edit: to clarify, what I mean is that th

Answer 1

Because compilers have to emit semantically correct programs. You can't memoize a function without changing program semantics unless it is referentially transparent. In most programming languages not all functions are referentially transparent (pure functional programming languages are an exception) so you can't memoize everything. But then a mechanism is needed for detecting referential transparency and that is too hard.