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The analogy is comparing writing programs to buying goods: | |
writing a program with static types is equivalent to buying | |
with cash, and writing a program with dynamic types is | |
equivalent to buying with credit. | |
The "cost" in either case is mental energy and time. When I | |
write a program with static types I spend a lot of effort up | |
front, guided by the type system and compiler, to handle edge | |
cases and generate a totally correct solution. I have to | |
fully-understand any libraries I'm using and characterize | |
the problem in terms of types. | |
When I write a program with dynamic types, I typically get | |
something I can run much faster, but then I struggle through | |
compose/test/debug cycles until the program is eventually | |
correct. The energy cost here is spread out (potentially | |
over days or weeks) instead of happening earlier. | |
The correct program is the thing I am buying in this analogy, | |
not the currency I'm spending. |
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Well, Spire is an interesting case. I mean, it's a big project, but as a library it's pretty modular. Also, there have been many collaborators (which is something a good type system has made way easier).