e.g.
a = foo(1) // evaluates, caches and returns value b = foo(1) // returns cached value c = foo (1) // returns cached value is optimized to a = b = c = foo(1) // evaluates, caches and returns value
Is pure meant to be a compiler hint so that it is up to the
programmer to enforce it? It is sometimes useful to maintain
hidden state for lazy evaluation, that does not affect purity
optimizations:
