Environments are intentionally not first class: that particular dynamic feature really sabotages optimization and can generally be worked around (e.g. instead o

Environments are intentionally not first class: that particular dynamic feature really sabotages optimization and can generally be worked around (e.g. instead of letting the full environment escape, expose a closure that mutates only what must be mutated). Julia has optional type annotations, but this doesn't mean that code without types is dynamic while code with types is static – all code is dynamic, the type annotations just limit the set of types that values can have. It's a subtle but important distinction.