Not impossible, but in my experience it takes disproportionately more work than if you have a decent type-system to help you out. In a dynamically typed system

Not impossible, but in my experience it takes disproportionately more work than if you have a decent type-system to help you out. In a dynamically typed system, every expression and line of code is a liability, and requires a large weight of tests to have any confidence that it might work.