The cost is up-front having to think carefully about types when you're not yet done exploring the problem space. Types, if you're going to use them, should be d

The cost is up-front having to think carefully about types when you're not yet done exploring the problem space. Types, if you're going to use them, should be decided on after you've completed that step. This is why if you're going to do it, a dynamically-typed language that allows adding hints/annotations later on is an ideal choice. And this is not a purely hypothetical objection: once you put types in a program, you're constraining the future of what you can do unless/until you go back and change them. Those constraints are a very real and, in my experience, very high cost.